Peripheral blood PCR for detection of Mycobacterium tuberculosis in patients with Hiv/Aids In Mumbai, India

Abstract

Background: Since the co-infection of Mycobacterium tuberculosis (MTB) and HIV is recognized as a lethal combination, there is need for a reliable diagnostic test that can be conducted on a readily available specimen such as peripheral blood to periodically screen HIV-infected individuals for MTB at an early stage. Methods: A study was designed to assess the diagnostic value of PCR targeted to IS 1081 in peripheral blood of HIV-infected individuals because of ease of obtaining periodic samples. A cohort of 129 individuals was recruited for this purpose. It contained of adult, non-pregnant HIV sero-positive as well as HIV sero-negative individuals who were naïve to anti-Koch’s treatment at two teaching hospitals in Mumbai. Results: The cohort of 129 individuals was categorized into 5 groups based on their clinical TB and HIV status. The mean CD4 count for TB+HIV+(Groups 1,2,3) ranged between 381 and 525 cells/cmm suggesting early to moderate immune suppression.TB PCR assay was compared with the ‘gold’ standard, namely the LJ culture in each of the 5 groups. Overall, the sensitivity of PCR was 83.3% and specificity was 97.1%. PCR+ LJ-were subjected to sequential TB PCR tests at intervals of two weeks after initiation of AKT.TB PCR+ patients converted to TB PCR negative between 6-8 weeks. Conclusions: The study established that PCR targeted to IS 1081 is a valuable test for early diagnosis of TB from peripheral blood at an early point of TB activation when most patients (>85%) did not produce other traditional specimens such as the sputum and/or pleural fluid.