HTB

Maternal TB, HIV and pregnancy

2 April 2010. Related: Conference reports, Women's health, Pregnancy, TB coinfection, .

Polly Clayden, HIV i-Base

Two posters looked at maternal TB in HIV positive pregnant women.

Amita Gupta and colleagues from the SWEN India Study Group assessed the effect of maternal TB (prevalent or incident) between pregnancy to 12 months post-partum on risk of HIV MTCT. [1]

The SWEN trial compared the use of extended NVP to single dose NVP among breastfed infants to reduce MTCT of HIV. [2] A secondary objective of the trial was to look at maternal and infant morbidity and risk factors for MTCT.

Maternal VL, CD4, duration of breastfeeding, type of ART intervention and maternal hepatitis coinfection are well known to be factors associated with HIV MTCT. The role of maternal TB however has not been well characterised.

The investigators used multivariable logistic regression to determine the impact of maternal TB on HIV MTCT. They used WHO criteria to define TB cases and manual methods for AFB smear and culture.

They found, out of 783 mothers, with a median duration of follow up of 365 days (IQR 346-368), median CD4 472 cells/mm3 (IQR 317-667; 7% <200 cells/mm3), 3 had prevalent TB diagnosed in pregnancy and 30 had incident TB by 12 months post partum.

When they looked at maternal TB and HIV transmission, they found among mothers with any TB the HIV transmission rate was 30.3% (10/33) compared to 11.6% (87/750) among mothers without TB (OR 3.3 95%CI 1.5–7.2, p=0.02). When they restricted the analysis to maternal TB diagnosed before HIV transmission this gave a transmission rate of 20.7% (6/29) among mothers with TB compared to 12.3% (91/754) among mothers without, (OR 1.9 95% CI 0.8–4.8, p=0.17).

Mothers with TB had a higher baseline viral load than mothers who did not (85,651 copies/mL vs 37,639 copies/mL, p<0.01).

In multivariate analysis, maternal TB was associated with an OR 2.4 (95%CI 1.0–5.98), for HIV transmission adjusting for maternal factors (viral load, CD4, AZT, NVP, HAART) and infant factors (breastfeeding duration, infant NVP, gestational age, birth weight) associated with MTCT of HIV.

The investigators acknowledged that this analysis had limitations including that as a secondary trial endpoint it was likely to be underpowered, not all TB diagnoses were culture confirmed so some misclassification bias was possible and unmeasured confounders could possibly explain this finding.

However they concluded that maternal TB appears to be an important risk factor associated with HIV MTCT but that, “larger studies are needed to confirm this and to understand the pathogenesis since this appears to be independent of maternal viral load and CD4”.

Celine Gounder and colleagues from the Perinatal HIV Research Unit performed a cross sectional study across six antenatal clinics in Soweto to look at provider initiated screening for TB among pregnant women.

The study included all pregnant women >18 years of age presenting to the clinics, who gave verbal consent to participate. Women presenting with obstetric complications or medical emergencies, who declined or were unable to provide verbal consent, and prisoners were excluded.

Regardless of their HIV status, women were screened for symptoms of active pulmonary TB ie, cough for >2 weeks, sputum production, fevers, night sweats or weight loss.

Information on their demographics, HIV status, CD4count, and prior TB and HIV history was also collected at the time of symptom screening.

Any woman with any symptom of active TB was then asked to provide a single sputum specimen, which was sent for sputum smear microscopy, mycobacterial
culture and identification, and INH/RIF drug-susceptibility testing.

The investigators reported that 3970 pregnant women were enrolled in the study between December 2008 and August 2009 who had a median age of 26 years (range 18-49).

Of these women, 1492 (36%) were HIV-positive. The percentages of women with CD4 count in the following strata at diagnosis were: 2% (0–50), 17% (51–00), 30% (201–350), 22% (351–500), 19% (>500), and 9% unknown (the investigator noted that 49% had a CD4 count of <350 cells/mm3). Additionally, 5% had a prior history of TB disease, and 21% had previously been exposed to someone with active pulmonary TB.

The investigators reported that the prevalence of active pulmonary TB was 696/100,000 among HIV-positive pregnant women (10/1492 cases), and 200/100,000 among HIV-negative pregnant women (5/2478 cases). They did not identify any cases of MDR-TB.

The investigators wrote: “Provider-initiated TB screening among HIV-infected pregnant women is a high yield intervention, and should be integrated with PMTCT services.”

They added: “Given that 49% of the women had CD4 T cell counts <350 cells/mm3, both ART and IPT should be considered in high TB/HIV prevalence settings.”

References

  1. Gupta A et al. Maternal TB is associated with increased risk of HIV mother-to-child transmission. 17th Conference on Retroviruses and Opportunistic Infections (CROI), 16-19 February 2010, San Francisco.  Poster abstract 899.
    http://www.retroconference.org/2010/Abstracts/37899.htm
  2. Gounder C et al. Provider-initiated screening for TB among pregnant women in antenatal clinics in Soweto, South Africa. 17th Conference on Retroviruses and Opportunistic Infections (CROI), 16-19 February 2010, San Francisco.  Poster abstract 900.
    http://www.retroconference.org/2010/Abstracts/37899.htm

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