Access to appropriate care and treatment is dependent on first diagnosing HIV and then managing the infection both on and off treatment.

For anyone over 18 months old, an initial HIV diagnosis is usually made using a rapid antibody test – of which there is quite an array of choices that are cheap, accurate, and easy to use within decentralised care.

CD4 tests are recommended for staging and monitoring the disease prior to initiating antiretroviral treatment – and for monitoring immune response to treatment, allowing opportunistic infection prophylaxis to be removed if higher CD4 counts are achieved – and viral load tests once treatment is started.

Because of passive transplacental transfer of maternal antibodies that can persist for up to 18 months antibody tests cannot be used for the accurate diagnosis of infants. So virological testing needs to be performed to determine an infant’s HIV status and enable immediate initiation of antiretroviral therapy (ART).

Although there are currently many options available for CD4 and virological testing, they are expensive and require sophisticated, centralised laboratories and trained technicians. To improve access to diagnostics in resource-limited settings and to make them affordable, they must be delivered as close as possible to the patient. A recent technical report from UNITAID describes a “diagnostic landscape” with high volume testing performed in centralised facilities (“super labs”) where feasible, and, most importantly, a drive towards decentralised point of care (POC) testing in harder to reach populations.¹

This chapter looks at the latter and describes promising POC technologies in the pipeline for CD4, viral load and early infant diagnosis (EID). These tests may be commercially available within the next couple of years. Many of the test sponsors appear to believe that their products will launch commercially next year. If their predictions come true then 2012 will be a bumper year for HIV POC diagnostics. The authors cannot guarantee that this bonanza will occur in 2012.

In order for a diagnostic test to be useful within a decentralised setting it should meet the WHO ASSURED criteria for the ideal rapid test, which is as follows:

• A = affordable
• S = sensitive
• S = specific
• U = user friendly (simple to perform in a few steps with minimal training)
• R = robust and rapid (results available in less than 30 minutes)
• E = equipment free
• D = deliverable to those who need the test

CD4 tests

The CD4 Initiative, based at Imperial College in London, was set up in 2005 to develop simple, instrument-free CD4 point of care tests designed specifically for rural areas in resource-limited settings.²

They began with a target product profile with a set of specifications that elaborate on the ASSURED criteria.

• Simple and robust
• Semi-quantitative, minimum cut off of 250 cells/mm3
• Stable at 40oC for 12 months
• Quality assurance material to check correct functioning of test
• Use of finger-prick blood/other non-venous blood sample
• Simple to perform, few steps and <2 hours training required
• <30 minutes from patient to result
• Simple read out
• All-in-one kit
• 25 tests performed/person/day
• Target price around $2 per test
• Customer capital outlay (if any) <$1,000
• Safe solution for infectious waste materials

In partnership with Zyomyx they have developed a fully quantative CD4 counter, that can be read visually without an electronic reader, much like a thermometer. It consists of a disposable cartridge with a mechanical spinner that requires no power supply. The test can measure an absolute CD4 count without complex instruments. Clinical trials are expected in 2011. If the results are positive, the test could begin to become available by 2012, according to Zyomyx.³

The Burnet Institute – who also worked on their prototype within the CD4 Initiative – is continuing to develop a rapid CD4 test in collaboration with the Rush University Medical Center and Duke University.⁴

This test is semi-quantative and will give a read out showing whether someone’s CD4 count is above or below a predetermined threshold – e.g., 350 cells/mm³. The user then can make a treat/don’t treat decision. Burnet is developing a reader for the device in collaboration with Axxin Ltd.

Clinical trials are planned in 2011 in the United States and Malawi. The further development and the launch of this test will depend on trial results and project funding.

Daktari Diagnostics is in late stage development of a portable CD4 cell counter. The device is a portable battery run instrument. Each CD4 test consists of a disposable plastic card, which is inserted into the instrument. The test measures absolute CD4 count.⁵

Validation studies in four African countries are expected to be underway this year. Follow-on studies in additional countries are also planned. The commercial launch is expected at the end of 2011.

MBio Diagnostics is developing a system that uses disposable cartridges and a simple reader instrument. It provides an absolute CD4 count.⁶

Field-testing in southern Africa is scheduled for later this year.

Table 1: CD4 point of care test pipeline

*Estimated cost

Viral load

The SAMBA (simple amplification based assay), is currently being developed by the Diagnostics Development Unit at the University of Cambridge.⁷

They are developing two tests, a semi quantative test for monitoring ART and a qualitative test for EID. The tests use isothermal amplification and visual detection by dipstick. SAMBA is being field tested by MSF in Malawi.⁸

The Liat TM Analyser, manufactured by IQuum, POC HIV assay is a real time, battery operated, small, portable, PCR kit. Blood is collected in a tube and inserted into the analyzer. Results are quantitative.

Clinical trials are scheduled for 2011 with the potential for launch in 2012.⁹

Alere NAT system is a generic platform designed to detect various nucleic acids. The first test – anticipated to be commercially launched next year – is a real time detection method for measuring quantative HIV RNA. The sample – which can be from finger-stick, whole blood, or plasma – is applied directly onto the disposable cartridge, which is processed by a compact, battery driven instrument.¹⁰

Table 2: Viral load point of care test pipeline

*Estimated cost

Early infant diagnosis

Virological testing or ultrasensitive p24 antigen testing should be used for EID. It is possible to use qualitative HIV RNA assays, as described above, as an alternative to HIV DNA. The SAMBA system is developing a test especially for this purpose.

North Western Global Health Foundation (NWGHF) is developing an HIV DNA-PCR test which is on hold – is not yet ready for field-testing – while the group focuses on a POC p24 test.¹¹

Both Micronics and BioHelix have DNA tests which appear to be in the proof of concept stage and are not ready for field-testing yet either.

The NWGHF p24 antigen rapid test consists of a plasma separator, reaction tube, reaction buffer, and rapid test strip. It is small, battery operated, and expected to be inexpensive. It has demonstrated about 95% sensitivity and 99% specificity.¹²

Clinical and field trials are expected to start this year and it should be available in 2012.

Table 3: p24 test for EID pipeline

*Estimated cost

References

1. Murtagh MM. HIV/AIDS Diagnostic Landscape. UNITAID Technical Report. May 2011
2. CD4 Initiative. Imperial College, London. http://www3.imperial.ac.uk/cd4
3. Zyomyx. http://www.zyomyx.com/index.php
4. Burnet Institute, Centre for Virology. http://www.burnet.edu.au/home/cvirology/clinicalresearchlab/projectsix
5. Daktari Inc. http://www.daktaridx.com/products
6. MBio Diagnostics. http://www.mbiodx.com
7. University of Cambridge. Department of Haematology. Diagnostics Development Unit. http://www.haem.cam.ac.uk/ddu
8. Malawi: SAMBA trial – Médecins Sans Frontières (MSF). http://www.msf-me.org/en/news/news-media/news-press-releases/ malawi-samba-trial.html
9. IQuum Products. http://www.iquum.com/products/productsdescr.shtml
10. Alere. http://www.alere.com
11. Northwestern Global Health Foundation. http://www.nwghf.org
12. McCormick. Northwestern Engineering. Centre for Innovation in Global Health Technologies. p24 Antigen Rapid Test for Pediatric HIV Diagnosis. http://www.cight.northwestern.edu/major_initiative/current%20projects1/p24_antigen_rapid_test.html.

Additional sources

• Murtagh MM. HIV/AIDS Diagnostic Landscape. UNITAID Technical Report. May 2011
  http://www.unitaid.eu/images/marketdynamics/publications/unitaid_md_technical_report_diagnostics_landscape_web.pdf
• Clayden P. Early infant diagnosis. HIV Treatment Bulletin. October 2010.
  http://i-base.info/htb/14000

The new WHO paediatric guidelines now recommend immediate antiretroviral therapy for children with confirmed HIV infection aged <24 months. However identifying HIV-infected infants and linking them to treatment programmes, particularly fast, is easier said than done.

DNA-PCR testing is generally used for early infant diagnosis (EID), but it is expensive and requires sophisticated, centralised laboratories and trained technicians. Although DNA-PCR has been used in resource-limited settings, its long turnaround time contributes to infant loss-to-follow-up and loss of benefit of immediate initiation of treatment. Currently, no point-of-care (POC) HIV tests are available for infants.

In a special session at IAS 2010, Susan Fiscus presented an excellent overview of the current tools available and the prospects of POC technology for early EID. [1,2]

She began with a list of desirable qualities for a POC diagnostic test:

• Rapid (< one hour)
• Sensitive (> 95%)
• Specific (> 98%)
• Inexpensive (<$5 per test)
• Simple (equipment: battery operated, few moving parts, small footprint/technique: minimum training required)
• Robust – no cold chain required
• Commercially available
• CE marked/FDA cleared

But she quoted Bill Rodriguez’s remark on the subject: “Cheap, fast or accurate. Pick two.”

The current tests used for EID are HIV DNA and total nucleic acid assays. The gold standard is the Roche AMPLICOR HIV DNA assay, version 1.5. This test is used in many countries and can use whole blood pellets or dried blood spots (DBS).

The Roche Qualitative Total Nucleic Acid Assay has also been introduced. This test works on whole blood and DBS. In one study it was shown to be 100% sensitive and 99.7% specific.

Abbott is also developing a DNA assay.

These tests need large, expensive equipment and are probably only suitable for sophisticated, centralised laboratories.

For resource limited settings, HIV DNA assays need to be POC. Dr Fiscus described three tests in development.

Researchers at the Centre for Innovation in Global Health Technologies (CIGHT) at Northwestern University are working on a POC DNA-PCR. At CROI in February, they reported a lower limit of detection of 5 copies/reaction and good sensitivity and specificity. [3] This assay uses a small, portable, battery-operated analyser, which can assemble the reaction and perform fluorescence detection and thermal cycling. The analyser card integrates DNA extraction, PCR reagent storage without refrigeration and PCR amplification.

Data from Micronics Real Time PCR was also presented at CROI 2010. [4] This assay uses a credit card sized device and microfluidic principles for both nucleic acids extraction and amplification. The investigators reported good sensitivity and specificity in this study.

The Biohelix Isolamp is another simple HIV DNA test under development. This assay couples helicase-dependent isothermal amplification (HDA) with amplicon detection using a disposable cassette. Early data were presented at the 2010 HIV Diagnostics Conference. [5]

She explained that the CIGHT test is not yet ready for field-testing and is on hold while the group focuses on a POC p24 test. Both the Micronics and BioHelix tests appear to be in the proof of concept stage and are not ready for field testing yet either.

It is possible to use qualitative HIV RNA assays as an alternative to HIV DNA. The qualitative Gen-Probe Aptima is the only HIV RNA test approved by the FDA for diagnosis. Although the FDA approval is for plasma or serum, this system works well with DBS. It is very sensitive and specific and is being used by the State of New York for EID.

She mentioned that it is unclear whether HIV RNA assays will be as sensitive when infants are being prophylaxed or if mothers are receiving antiretrovirals and breastfeeding the child.

Several other HIV viral load assays are currently commercially available, but are not POC, require large expensive equipment, and are suitable for centralised laboratories.

Dr Fiscus described three POC RNA assays that are in development. The SAMBA (simple amplification based assay) is currently being developed by the University of Cambridge and Diagnostics for the Real World. Data were recently published in JID. [6] This test uses isothermal amplification and visual detection by dipstick. It has a limit of detection of 75 copies/mL using 250 mL of plasma, and 400 copies/mL using 100 mL whole blood. No cold chain is required and it can be battery operated. It is simple to operate and little training is needed. There will be a clinical trail for regulatory approval in 2011.

Dr Fiscus showed recent unpublished data from her own research group. The IQuum LIAT quantative POC HIV assay is a real time PCR, which can be battery operated, is easy to use and requires little training. It gave 92% correlation with Abbott m2000 with 75 plasma samples. It has not yet been tested with whole blood. The assay takes 60 minutes to perform but does need a cold chain.

Inverness Medical Innovation’s CLONDIAG, uses a microarray, real time detection method. It can use fingerstick, whole blood or plasma. The sample is applied directly onto the test cartridge, which is processed by a compact, battery driven instrument. Preliminary data provided by the manufacturer are promising.

Finally p24 antigen tests, which have limited use in adult diagnostics, can be used for EID. The ultrasensitive, heat dissociated p24 antigen assay has been shown to work well with both plasma and DBS.

As far as POC is concerned, Dr Fiscus showed results from the CIGHT p24 antigen rapid test that were recently published ahead of print in JAIDS. [7] This assay is performed, by adding 25mL of plasma to 75mL buffer. This mixture is heated in a water bath at 90 degrees for four minutes. A test strip is then inserted and gives a read out after 20 minutes. Trials in Cape Town showed 95% sensitivity and 99% specificity.

She also described an improved CIGHT POC p24 antigen rapid test under development. This assay uses whole blood and heat shock to increase sensitivity. It consists of a plasma separator, reaction tube, reaction buffer and rapid test strip. It is battery operated and each test should cost $1-2.

In keeping with Bill Rodriguez’s remark she presented the most likely future tests in a table. See Table 1.

Table 1: ‘Cheap, fast or accurate. Pick two” Susan Fiscus

She concluded that promising POC assays for EID today include: IQuum’s LIAT, SAMBA, CIGHT p24 and possibly CLONDIG’s viral load assay.

comment

This was an incredibly useful overview and it looks like we can be optimistic about having a POC test for EID in the next couple of years.

Other presentations at the conference dealt with the challenges of access to EID. In the same session, Shaffiq Essajee noted that EID access has improved and in some countries more than 50% of exposed infants are tested. [1] But infant testing is usually linked to PMTCT and if coverage is low, so is infant testing coverage. Globally only 15% of exposed infants get a test. Even when there is access to EID, infected infants do not necessarily get ART.

Laura Guay showed that there are similar coverage cascades with EID to that of PMTCT. [8] Losses occur at each step of the cascade. She showed data from a programme of the Elizabeth Glaser Pediatric AIDS Foundation in which there were 4226 infants with known exposure. Of these 4099 (97%) had EID drawn, 895 (70%) had results returned from the lab with 449 (15%) positive results. Then only, 230, (51%) received results, 200 (87%) enrolled in care and 178 (89%) infants initiated treatment. Overall, she explained, there were 633 infected children, of which 71% were identified and 28% treated. “And this” she said “is a good programme”.

A related poster showed Ministry of Health data from 84 sites in Cambodia, Namibia, Senegal and Uganda with >21,000 infants tested. [9] Although the study was called “Increasing uptake of HIV early infant diagnosis services in four countries” and showed steady increases in sample volume, in 2008, it was still low in three of the countries reviewed: Cambodia 14%, Senegal 9% and Uganda 21%. Namibia however achieved 86-100% EID coverage. Less than half these infants ever tested via EID were tested in their first two months of life. Coverage of optimal service (early testing) is consequently even lower. And of those infants tested HIV positive via EID, attrition is significant 72%, 67% and 67% were not alive and on ART in Uganda, Cambodia and Senegal respectively.

The investigators concluded: “Significant strides to establish and increase access to and uptake of EID testing have been made across all countries reviewed. When decentralising, it is important for programming to focus on early identification and access to the full package of exposed infant services including EID.”

So as well as a POC test for EID, which will take care of some of the obstacles to successful diagnosis and treatment, programmes need to ensure good systems for patient management and links between services to ensure that they can take full advantages of the promise of these new technologies.

References

1. Scaling Up Early Infant Diagnosis of HIV as the Bridge between Prevention, Care and Treatment: Successes, Challenges and Potential Solutions. 18th IAS. July, 2010. Vienna. Special session SUSS03.
   http://pag.aids2010.org/session.aspx?s=150
2. Fiscus S. EID – current tools and prospects of point of care technology. 18th IAS. July, 2010. Vienna. Special session SUSS0302.
3. Jangam S et al. A point-of-care DNA PCR test for infants. 17th CROI. February 2010. San Francisco. Poster abstract 891.
4. Granade T et al. rapid extraction and amplification of HIV-1 DNA from whole blood using a disposable microfluidics device. 17th CROI. February 2010. San Francisco. Poster abstract 945.
5. Jordan JA et al. Evaluation of the IsoAmp HIV detection kit using whole blood samples. HIV Diagnostics Conference, March 24-26, Orlando, Florida. Poster abstract 34.
6. Lee H et al. Simple Amplification-Based Assay: A nucleic assay based point-of-care platform for HIV-1 testing. Jour Infect Dis 2010:201 (Supp 1) S65-72.
7. Parpia ZA et al. p24 antigen rapid test for diagnosis of acute pediatric HIV infection. J Acquir Immune Defic Syndr. Published ahead of print August 2010.
8. Guay L. Early infant diagnosis of HIV: successes, challenges and potential solutions. 18th IAS. July, 2010. Vienna. Special session SUSS0301.
9. Tripathi S et al. Increasing uptake of HIV early infant diagnosis (EID) services in four countries (Cambodia, Namibia, Senegal and Uganda. 18th IAS. July, 2010. Vienna. Poster abstract TUPDB205.
   http://pag.aids2010.org/Abstracts.aspx?SID=185&AID=14996

The ARCHITECT HIV Ag/Ab Combo Assay is the first HIV diagnostic assay to be approved in the US that detects both antigen and antibodies for HIV.

The new test is also the first diagnostic test approved by FDA for use in children as young as 2 years of age, and pregnant women.

It is specific for the detection of the HIV-1 p24 antigen (the substance found on the virus that triggers the production of antibodies), as well as antibodies to HIV-1 groups M and O, and as antibodies to HIV-2.

Levels of p24 antigen increase early after initial infection, before HIV antibody is produced and extends diagnosis to earlier, acute phase (recent) infection with HIV, reducing the window period (that period after initial infection and before the detection of infection based on formation of detectable antibodies).

The median detection time was demonstrated to be 7 days earlier (range 0 to 20 days) compared to 3rd generation enzyme immunoassay antibody tests.

comment

Fourth generation tests have been widely used in Europe for many years, although a handful of clinics, still use third generation despite current guidelines.

Although these tests reduce the window period between potential exposure and the opportunity to test down to 2–3 weeks, from a public health perspective, 28 days/4weeks is now possible.

Testing guidelines still refer to a six-week window by which time p-24 which peaks before 3 weeks and disappears after 2–3 months, is already fading.

Despite the widespread use of fourth generation testing, it is difficult to understand why many clinics in the UK still routinely refer to a three-month window period. This not only prolongs the anxiety for anyone who is concerned about recent exposure, but also undoubtedly misses the opportunity to diagnose some people during early infection. Many people who are concerned enough to test early, may be less likely to test three months later once their initial anxiety has abated, especially give the sometimes difficult access to walk-in, same day and out-of-hours testing services.

The British Association for Sexual Health and HIV (BASHH) guidelines on HIV testing state: [2]

“Fourth generation tests will detect the great majority of individuals who have been infected with HIV at one month (4 weeks) after specific exposure.”

“Patients attending for HIV testing who identify a specific risk occurring more that 4 weeks previously, should not be made to wait three months (12 weeks) before HIV testing. They should be offered a 4th generation laboratory HIV test and advised that a negative result at 4 weeks post exposure is very reassuring/highly likely to exclude HIV infection. An additional HIV test should be offered to all persons at three months (12 weeks) to definitively exclude HIV infection. Patients at lower risk may opt to wait until three months to avoid the need for HIV testing twice.”

References:

1. FDA list serve announcement. (18 June 2010).
2. The British Association for Sexual Health and HIV (BASHH) statement on HIV window period (15 March 2010).
   http://www.bashh.org/guidelines

The effectiveness of antiretroviral treatment delivery was traditionally thought to depend on the use of sophisticated diagnostic tests.

Earlier this year, important findings from the Development of AntiRetroviral Therapy in Africa (DART) trial, conducted in Zimbabwe and Uganda were published, showing impressive survival rates in people receiving routine clinical monitoring alone. This trial randomised patients to receive either clinical monitoring or laboratory (hematology, biochemistry and CD4) plus clinical monitoring. At five years, 87% and 90% of patients were alive in the clinical and laboratory arms respectively. [1]

These results were even more impressive as patients in this trial had a median baseline CD4 count of 86 cells/mm3.

The DART investigators concluded that ART could be delivered safely with good quality clinical care, allowing treatment delivery to be decentralised. Despite DART results being occasionally misinterpreted to suggest that this argues for no monitoring at all, the investigators also recommended that there is a role for CD4 testing from the second year on ART to guide the switch to a second-line regimen–and clearly to start treatment. They added that this should encourage accelerated development of simpler, cheaper, point-of-care CD4 tests.

Furthermore, in an accompanying editorial, Andrew Phillips and Joep van Oosterhout argue that, although the authors suggest that the advantage of measuring viral load on survival may have been modest in this cohort, the reduction of transmission of drug-resistant virus, which will undermine the effectiveness of antiretroviral therapy over the longer term may be another reason to measure it. “Therefore development of cheap robust assays for viral load that can easily be used in rural and urban settings is of the highest priority for researchers.”

There are many arguments for the development of affordable point of point-of-care assays. CD4 measurements are essential for knowing when to initiate ART. CD4 counts also guide the use of opportunistic infection prophylaxis.

Viral load testing is essential to diagnose HIV-infected infants (see next chapter) and to monitor virological suppression in pregnant women to reduce the risk of mother to child transmission. These tests can be used to monitor adherence early on, and better inform decisions about treatment modifications or switches. [3, 4]

The next edition of the Pipeline Report will include a more detailed survey of diagnostics appropriate to low resource settings. Here we look at the qualities required from a point-of-care test to be useful and two initiatives that appear to be close to emerging from the pipeline.

Requirements for point-of-care tests

Point-of-care refers to a test that can be conducted in the same facility where a patient receives his/her treatment and other care. In rural areas many patients have to travel vast distances to reach testing facilities and then return to get their results. There is considerable loss to follow up from people who do not return for their test results.

These technologies need to be quick and easy to use and interpret, that work with a finger-prick blood sample or other non-venous sample and have a simple read out. They need to be appropriate to settings without sophisticated laboratories, where electricity and running water cannot be guaranteed. They need to perform in hot, humid or dusty environments and have a long shelf life. They need to be used and maintained by health workers without advanced technical skills.

The CD4 initiative point-of-care CD4 test

The CD4 Initiative, at Imperial College, was established in 2005. The Initiative came about through a substantial activist push from Gregg Gonsalves, and a generous grant from the Gates Foundation. [5]

Led by principal investigator Dr Hans-Georg Batz and project manager Dr Steven Reid, their objective is to develop new, low-cost, rapid point-of-care tests to measure CD4 counts, which are suitable for use in rural areas of low-income countries.

The initiative set out to produce tangible results in four years, which is a very ambitious timescale to develop this type of product.

The project began by establishing a set of predetermined specifications:

• Simple and robust
• Semi-quantitative, minimum cut off of 250 cells/mm³
• Stable at 40ºC for 12 months
• Quality assurance material to check correct functioning of test
• Use of finger-prick blood/other non-venous blood sample
• Simple to perform, few steps and <2 hours training required
• <30 minutes from patient to result
• Simple read out
• All-in-one kit
• 25 tests performed/person/day
• Target price around $2 per test
• Customer capital outlay (if any) <$1,000
• Safe solution for infectious waste materials

Phase I of the project was proof of concept, in which new tests were developed, that can reliably measure CD4 counts in blood. Phase II involved developing prototypes, scale-up and validation. That is, to establish whether the new tests met most, if not all, of the specifications and provided reliable and reproducible results in medium-scale production.

In Phase III the tests will be trialled in resource-poor settings to make sure that specifications are achievable in field conditions. The costs will also be evaluated. The group has completed two rounds of independent verification using samples from clinics in London. Field-testing will start later this year in Malawi and Uganda.

Three prototypes (Beckman Coulter, Burnet Institute and Zyomyx Inc.) were assessed against the gold standard method of measuring CD4 counts called flow cytometry. Flow cytometry is a technique for counting CD4 cells by suspending them in a stream of liquid and passing them by an electronic detector. The machines used to perform these tests are big and expensive and require an uninterrupted supply of electricity and highly trained technicians.

This verification trial used around 150 blood samples from HIV-positive patients in London to see if the same results could be obtained with the prototype tests as with flow cytometry. The results showed that only the test from Zyomyx, Inc compared favorably with flow cytometry. The other two tests failed to correctly identify samples from patients with low CD4 counts with sufficient sensitivity, thus the initiative is proceeding with the Zyomyx Inc., point-of-care CD4 test.

Zyomyx is based in San Francisco. The device is a CD4-gauge “much like a thermometer” and this simple test will be able to provide a quantitative CD4 count from a finger-prick of blood—exceeding the original specif ication of semi quantitative with a minimum cut-off.

After the field-testing, phase IV of the project will be technology transfer (ideally in the developing world), large-scale production and distribution.

This test can be used for both adults and children with a different measuring range for younger children and infants.

Point-of-care viral load test

The Diagnostics Development Unit based at the Department of Haematology, University of Cambridge, and led by Dr Helen Lee, are developing a simple amplification based assay (SAMBA). This is a nucleic test based on visual detection of viral nucleic acid by dipstick designed to detect a broad range of HIV-1 subtypes typical to sub-Saharan Africa. [6]

Like the CD4 Initiative, the group conducted a survey of potential users in resource-limited settings. Again, respondents need tests that are quick and simple and can be performed while patients are at the clinic. The SAMBA needs to be, “simple, robust, inexpensive, stable and self contained with predispensed unit-dose reagents and disposables included and with a design and procedure that comply with biosafety standards”.

Recent data published in the April 2010 supplement of the Journal of Infectious Diseases showed the sensitivity and subtype coverage of the SAMBA test, when tested with 69 samples provided by The Royal London Hospital, to be at least as good as those of commercially available diagnostic tests.

The investigators suggested that the SAMBA system is not restricted to HIV and could also be adapted to detect other infections.

References

1. The DART trial team. Routine versus clinically driven laboratory monitoring of HIV antiretroviral therapy in Africa (DART): a randomised non-inferiority trial. The Lancet, Volume 375, Issue 9709, Pages 123-131, 9 January 2010.
2. Phillips A and van Oosterhout J. DART points the way for HIV treatment programmes. The Lancet, Volume 375, Issue 9709, Pages 96-98, 9 January 2010
3. Calmy A et al. HIV viral load monitoring in resource limited regions: optional or necessary/ Clin Infect Dis 2007; 44(1):128-134
4. Usdin M et al. Patient needs and Point-of-Care Requirements for HIV Load Testing in Resource Limited Settings. J Infect Dis 2010 (suppl 1) 573-577
5. The CD4 Initiative. Accessed July 5, 2010 from:
   http://www1.imperial.ac.uk/medicine/about/divisions/departmentofmedicine/infectiousdiseases/infectious_diseases/cd4_initiative/
6. Lee H H et al. Simple Amplification-Based Assay: A Nucleic Acid-Based Point-of-Care Platform for HIV-1 Testing. Jour Infect Dis 2010:201 (Supp 1) S65-72.

The US Food and Drug Administration has approved a new, single-use 10 dollar, 10 minute HIV-1 antibody test, the Uni-Gold Recombigen, made by the Irish company Trinity Biotech PLC. It is the first testing kit to be approved by the FDA for use in plasma, serum and whole blood (venipuncture). The 20-minute OraSure test can be used only on whole blood.

The device, which tests a single drop of whole blood, serum or plasma, is only allowed to be used by clinical laboratory professionals in facilities that have suitable quality assurance programmes and Trinity Biotech wants to sell it to government programmes, physicians and hospitals for use following needlestick injuries and to test pregnant women. People being tested must receive printed information and counselling, and positive tests require confirmation. The company hopes to sell nearly 500,000 in the US this year alone. The test is already sold in Africa and Asia.

The FDA based its approval on company research involving more than 9,000 patient samples that detected 100% of HIV-positive specimens, and was 99.7% accurate on the negative samples.

Links:

Trinity Biotech
http://www.trinitybiotech.com/EN/index.asp

FDA
http://www.fda.gov/

Product labeling will be available at
http://www.fda.gov/cber/products/testkits.htm

A cost comparison of three HIV testing technologies, conducted by researchers at the US Centres for Disease Control and Prevention and other institutions, concludes that rapid test protocols offer economic advantages as well as convenience, compared to the standard testing protocol. Donatus U Ekwueme and colleagues present cost estimates that should prove helpful to HIV programme managers and other public health decision makers who need information on these counselling and testing technologies.

More than 2 million HIV tests are performed each year at publicly funded clinics in the US. Clients do not receive results of one third of these tests because they don’t go back to the clinic for them. Results of standard tests can take up to two weeks, but the use of newer, rapid tests improves the number of people who learn their test results. The researchers write that no study has systematically compared the costs of these newer technologies with standard tests so they compared three HIV counselling and testing protocols: the standard protocol and the one-step and two-step rapid protocols.

They calculated the intervention costs of counselling and testing services with each type of protocol and found that the one-step rapid protocol was generally the least expensive of the three. They also report: “The standard protocol cost less than the two-step protocol per HIV-positive client notified of his or her HIV status, but cost more per HIV-negative client. The sensitivity analysis indicated overlap in the cost estimates for HIV-negative clients, reflecting the generally similar costs of the three testing protocols. Taking into account HIV seroprevalence, the two-step rapid protocol would be less expensive than the standard protocol for most publicly funded testing programs in the United States.”

Ref: Ekwueme D, Pinkerton S, Holtgrave D et al. Cost comparison of three HIV counseling and testing technologies. American Journal of Preventive Medicine (08.03) Vol. 25; No. 2:112-121
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12880878&dopt=Abstract

CD4 cell count and CD4 cell percentage are key markers for determining disease progression and risk for opportunistic infection in HIV-infected patients.

These markers are of greatest use in treating the asymptomatic patient, in whom disease stage is more difficult to assess clinically and for whom laboratory measurements serve as guidelines for the initiation of therapy and opportunistic-infection prophylaxis.

However, providers in resource-constrained settings may not have access to this laboratory measurement or its cost may be prohibitive, resulting in the need for an alternative, surrogate marker. Given the decreasing costs and increased availability of antiretroviral therapy (ART) in the developing world, this is an issue of critical and increasing importance.

A number of previous studies indicate that the total lymphocyte count (TLC) may be useful as a surrogate marker of immune status in certain settings. However, controversy regarding the utility of the TLC remains.

A variety of recent small studies have sought to determine the utility of the TLC in predicting the stage of HIV disease. The majority of these studies indicate a positive correlation between TLC and CD4 cell count, although the specific data on correlation coefficients, sensitivity, specificity, and positive predictive value (PPV) have been mixed. In addition, the patient populations examined, parameters measured, and methods used for statistical analysis vary widely among the different studies.

TLC may have a role both in decisions about the initiation of ART and in the monitoring of immunologic response to ART in resource-constrained settings. There has been a wide range of findings in published studies, many of which have included small numbers of patients.

To summarise, a total of 15,102 patients enrolled in 15 different studies have been followed up to determine the ability of the TLC to predict the CD4 cell count and HIV disease stage. Eleven of these studies (which included a total of 11,713 patients) contained data that, overall, indicated support for the predictive ability of the TLC, whereas four have concluded that the TLC was not a reliable predictor of the CD4 cell count.

In contrast, only three different studies, with a total of more than 440 patients, have attempted to evaluate the use of TLC in monitoring the response to ART. All of these studies have produced data that, overall, support the use of TLC as a surrogate marker for CD4 cell count in monitoring patients receiving ART.

The authors conclude, “More convenient and less expensive technologies are needed as alternatives to currently available CD4 cell assays in resource-limited settings. Political pressure has been successful in reducing the cost of ART, and it needs to be extended to advocacy for reducing the cost of determining HIV disease stage and monitoring therapeutic outcomes.”

Ref: Schreibman T, Friedland G. Use of total lymphocyte count for monitoring response to antiretroviral therapy. Clinical Infectious Diseases 38:257-262. January 15, 2004.
http://www.hivandhepatitis.com/recent/test/lymphocyte/011204_b.html

CDC recommendations

In April, The US Centres for Disease Control and Prevention (CDC) released a revised HIV/AIDS prevention strategy, which targets the estimated 200,000 people in the United States who are HIV-positive but are unaware of their status. The agency urged local health departments to use the rapid HIV test — which was approved by the FDA in November 2002 for use in about 40,000 hospitals and clinics with laboratories — in all federally funded clinics, as well as places such as homeless shelters, jails and substance abuse treatment centres.

In February, President Bush announced expanded availability for OraSure Technologies’ OraQuick HIV test, which offers results that are 99.6% accurate within 20 minutes, to more than 100,000 doctors’ offices and public health clinics. AIDS groups had advocated making the test more widely available to the general public. The CDC also recommended simplifying the pre-test counselling process. However, the CDC does not yet have recommendations on the use of the rapid test or what type of counselling should accompany the test, leaving such decisions up to local health authorities.

Working in counselling

The speed and portability of the new HIV test means that some people may find out they are HIV-positive in places where counselling and other services may not be immediately available, Fred Swanson, executive director for Gay City Health Project, said. Local health officials say that they can successfully combine counselling and testing in public locations.

The health department has drafted its own protocols for using the rapid test. “Our big challenge, and one of the big goals for the Centres for Disease Control, is to try to increase the number of people with HIV infection who know that,” Chaffee said, adding, “One, because people who have HIV and don’t know it are losing the benefits of good medicine. … And two, we know from a variety of studies that when people know they have HIV infection, they are much more careful with their sexual and needle-sharing partners.”

Although Washington state law requires pre- and post-test counselling, the law is not specific as to what the counselling should entail, according to the Globe. “Are recipients of positive test results going to be able to internalise the information they’ve received around the (new) test when they don’t have any time to mull the information over?” Paul Feldman of Seattle’s Lifelong AIDS Alliance asked. Swanson said that although he is worried about possible negative effects of using the rapid test in public settings, he said that he is reassured by the fact that the rapid testing will not occur immediately in gay bathhouses and sex clubs. “What’s exciting to me is that the local health department recognizes that there may be some challenges, and as such is doing a trial run,” he added (Boston Globe, 5/30).

Source: Kaiser Daily HIV/AIDS report

http://www.kaisernetwork.org
http://www.kaisernetwork.org/daily_reports/rep_index.cfm?DR_ID=18002

Boston Globe
http://www.boston.com/globe/

Quality Assurance Guidelines for testing using the OraQuick Rapid HIV-1 Antibody Test has just been published on the HIV/AIDS Prevention web site. This PDF document is available at
http://www.cdc.gov/hiv/rapid_testing/materials/QA_Guidlines_OraQuick.pdf

The document’s appendices, which discuss government regulations and provide sample forms, are available at
http://www.cdc.gov/hiv/rapid_testing/materials/QA_Guidelines_OraQuick_Appendix.pdf

comment

Although receiving an HIV diagnosis is still a traumatic event, the medical reality has changed significantly from the 1980s when many testing protocols were first developed. From an individuals’ medical perspective an earlier diagnosis allows both better medical intervention, including accurate detection of infection with drug-resistant virus.

Rapid tests have been available for several years in the UK (Abbott, Determine) but still have not been widely adopted – even though the unit cost is very low. This produces a result within 20 minutes from a fingerprick sample and allow patients to receive results within an hour. This minimises the stress associated with the delay of receiving test results which in the UK still routinely take up to a week. They also increase the percentage of people who return for their results which, again in the UK, can be as little as 35%.

From a public health perspective this would reduce risk of further infections, which may be largely driven by people unaware of their HIV status, especially considering the high viraemia associated with recent infections. Pre and post test counselling can still be provided in this setting, with people receiving an HIV-positive diagnosis more likely to benefit from more significant support.

Including HIV and hepatitis within the routine serology testing at GUM clinics, with HIV becoming an ‘opt-out’ rather than ‘opt-in’ test, increased uptake of HIV testing from 35% to 65% in one study, and identified two cases of previously undiagnosed HCV.

http://bmj.com/cgi/content/full/326/7400/1174

HIV testing with results within an hour is already available in the UK in very few clinics (John Hunter, London Lighthouse, Victoria Clinic and Soho clinic for gay men). Pre-test counselling and offer of follow-up counselling is provided as required.

China and the United States have both approved a rapid, portable HIV testing kit that is cheap to produce, easy to use and gives results in three minutes. It is being compared to home pregnancy tests and could revolutionise HIV testing. After receiving distribution approval from China’s State Drug Administration in February, a small Canadian biotech company is rushing to produce 400,000 rapid HIV tests for the nation. “The Chinese government has finally acknowledged this is a problem. Now they’re trying to make prevention a priority,” said Daniel Sham of the company MedMira. The US Food and Drug Administration approved the test in April.

The test, which costs about US$2.25 to manufacture, detects antibodies in the blood and shows two red lines for a positive result. Unlike conventional HIV tests, MedMira’s test produces results in about three minutes. The Chinese order is for 400,000 tests to be distributed to clinics and hospitals.

The company said in a statement: “With the FDA approval, MedMira can market the Reveal Rapid HIV-1 Antibody Test for the detection of HIV-1 antibodies in serum or plasma. This test has a one-year shelf life at room temperature, the longest of any rapid HIV tests available in the United States. MedMira’s test also produces highly accurate results substantially faster than any other FDA-approved HIV diagnostic test.”

Stephen Sham, Chairman and CEO of MedMira, said: “We are very pleased to enter the United States market with the best rapid HIV test to date. Many countries view the approval to market of a diagnostic test by the FDA to be the gold standard of endorsement. Now that we have obtained this approval, we are very optimistic about the immediate expansion of MedMira’s operations. We look forward to fulfilling the global diagnostic marketplace with our unique diagnostic products.”

Sham called the earlier approval by China a landmark event for his company, which was founded in a university basement a few years ago. “This regulatory approval achieves one of the company’s strategic goals of gaining access to large markets where the power of our technology can be used to make a difference in a significant public health campaign,” he said.

Chinese HIV infection rates have surged, particularly in remote regions where IV drug use, prostitution, migration and blood transfusions have increased. In addition, China’s blood supply was largely unregulated in the 1980s and many private agencies mixed supplies, reused needles and operated without sterilised equipment.

MedMira – which also manufactures diagnostic tests to detect hepatitis – signed a deal recently to supply 1 million tests to the Democratic Republic of Congo. Health Canada approved the test in 1998.

http://www.medmira.ca/news11.htm

The study, published in the Lancet, indicates that the new tests detected latent infections more accurately than the standard skin-prick test used for a century.

The tuberculin skin-prick test is the cornerstone of TB control in developed countries, but it has many drawbacks. It involves injecting a substance under the skin on the arm and a technician reading the resulting bump a few days later. The test can give false positive readings in people who have had the BCG TB vaccine because antibodies are made in both cases.

The new test, developed by scientists at Oxford University in England, is a blood test using a different substance to stimulate a reaction. Instead of looking for antibodies, it detects the activation of immune system T-cells.

Researchers compared the new test with the skin-prick test on 535 children at a British school where a student was diagnosed with TB in 2001. Children who were exposed to the student with TB were significantly more likely to test positive with the new method, the study found. While the skin test was more likely to be positive in BCG-vaccinated children than in non- vaccinated children, there was no link with vaccination in the new test. The two tests reached the same conclusion in 89 percent of the children. When the results did not match, it was impossible to know for certain which test was correct. However, when the new test was positive and the skin test was negative, this was a strong predictor of TB exposure in the children. When the results were reversed, this was not a strong indicator of a child’s exposure to TB – suggesting that isolated positive results from the blood test were more likely to be true positives than isolated positive results from the skin test, the scientists said.

Dr. Mark Perkins, a TB specialist at the World Health Organization, said about 95 percent of TB cases occur in the developing world, where a new diagnostic test for active TB is crucial because the current technology detects less than one- third of cases.

Ref: Ewer K, Deeks J, Alvarez L et al. “Comparison of T-cell-based assay with tuberculin skin test for diagnosis of mycobacterium tuberculosis infection in a school tuberculosis outbreak,” is published in the Lancet (2003;361(9364):1168-1173)
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12686038&dopt=Abstract