High rate of lost and untested TB biopsy samples and low screening for latent TB

8 June 2009. Related: Conference reports, TB coinfection, BHIVA 15th Liverpool 2009.

Simon Collins, HIV i-Base

E Elliot from the Lawson Unit in Brighton presented one of several interesting papers looking at practical aspects of efficiency and care, in this instance, the appropriate testing of biopsy samples. [1]

The group identified all tissue sampling undertaken on HIV-positive patients by reviewing hospital coding records from 2003 to 2008 and weekly ward lists from 2006 to 2008 and cross referenced this with records on the pathology database. Four consultants independently identified samples that should have been sent to microbiology.

Of the identified 62 samples that would be expected to go to microbiology, all were sent to histopathology but only 20 were also sent to microbiology. Out of 42 samples that were not sent to microbiology, request forms in 28 clearly stated TB or other infection as a potential diagnosis. Of these 42 samples, 13 samples from 12 patients subsequently had mycobacterial (n = 9) or other infection identified on blood cultures, re-sampling or histology.

The researchers concluded that more than a third of tissue samples in HIV patients were sent to microbiology, and this resulted in many missed or delayed diagnoses and that the hospital is now developing clearer clinical pathways for tissue biopsy.

The importance of latent TB diagnosis, through a more comprehensive screening of newly HIV-diagnosed African patients, was reported by Okpaluba and colleagues from Leeds Teaching Hospitals. [2]

Of 101 new HIV-diagnoses, 70% were in African patients, but only 24/70 patients were tested for TB either at HIV diagnosis or through other screening programmes. In these patients, 4/24 samples were found to be abnormal and 3 people were treated for latent TB.

This study highlighted both the sub-optimal screening in a high-risk patient group, together with the cost effectiveness of treating latent TB and using the immune-based interferon-gamma (TB Quantiferon Gold) testing for diagnosis.

References:

1. Elliot E et al. Tissue biopsy in HIV-infected patients: how often do samples get sent for microbiological analysis? 15th Annual Conference of the British HIV Association (BHIVA), 1-3 April 2009, Liverpool. Poster abstract 124.
2. Okpualuba U et al. Introducing a protocol for diagnosing and treating latent TB in newly diagnosed HIV patients: feasibility and cost effectiveness. 15th Annual Conference of the British HIV Association (BHIVA), 1-3 April 2009, Liverpool. Poster abstract P72.