Peripheral Blood PCR For Detection Of Mycobacterium Tuberculosis In Patients With HIV/AIDS In Mumbai, India

摘要

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 na?ve 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. Background The World Health Organization (WHO) estimates that over 2 billion individuals globally are infected with Mycobacterium Tuberculosis (MTB) (1). While MTB continues to be a major cause of morbidity and mortality in developing countries, there has been a resurgence even in developed countries where it was successfully contained (2). The situation is further compounded by emergence of MDR and XDR-TB (3,4). With the advent of the HIV/AIDS pandemic and its consequent immune suppression, the coinfection of TB/HIV is now recognized as a lethal combination (5). Such co-infection occurs in at least 60-70% of HIV-infected individuals during their lifetime leading to their rapid HIV-disease progression and death (1, 5). The existent diagnostic tests for MTB in developing countries such as microscopy that lacks sensitivity, LJ culture that takes 6-8 weeks to produce a result, or Bactec 460 assay that takes 10-14 days are not very helpful. Consequently, the authors felt that there was a 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 of infection (6, 7). Polymerase Chain Reaction (PCR) assay is a more sensitive, specific and quicker method for detection of MTB in clinical specimens (8, 9). Early diagnosis of TB co-infection will help reduce morbidity, mortality and further immunologic damage in HIV-infected individuals. Patients and Methods PCR targeted to insertion sequence (IS) 6110 has been successfully used for detection of Mycobacterium tuberculosis(MTB) in cerebro-spinal fluid in India (10). The authors designed a study to assess the diagnostic value of PCR targeted to IS 1081 in peripheral blood of HIV-infected individuals. An earlier study from India reported that IS 1081 to be prevalent in >80% in the study group (7). The study used peripheral blood because of ease of obtaining periodic samples. Between February 2006 and January 2008, a cohort of 129 individuals was recruited for this purpose (Table I). It contained of adult, non-pregnant HIV sero-positive as well as HIV sero-negative individuals who were na?ve to anti-Koch’s treatment (AKT) and attending the Department of Infectious Diseases (DID) MGM Medical College, Navi Mumbai and KJ Somaiya Medical College, Mumbai. All HIV+ patients were tested for CD4 counts using flowcyto-