The performance of quantiferon-TB gold in-tube (QFT-IT) test compared to tuberculin skin test (TST) in detecting latent tuberculosis infection (LTBI) in the presence of HIV coinfection in a high TB-burden area with BCG-vaccinated population.

OBJECTIVES: To compare quantiferon-TB gold "in tube" (QFT-IT) with the conventional tuberculin skin test (TST) for the diagnosis of latent tuberculosis infection (LTBI) in HIV-infected adults in a setting highly endemic for tuberculosis with BCG vaccinated population in Bangalore, Karnataka, India. PATIENTS AND METHODS: The study population (100 BCG-vaccinated adults) was divided into 4 groups: HIV patients with TB patient contact, HIV patients with past history of TB, TB patients (positive control), and healthy volunteers (negative control). RESULTS: Overall agreement between TST and QFT-IT was 52.4% (κ = 0.22). Increasing the TST cutoff value from 5 mm to 10 mm among HIV-positive groups resulted in better agreement 62.5% in Group 1 and 81.2% in Group 2. DISCUSSION: In a setting with high TB prevalence, the TST gives increased false positives in HIV-positive groups if 5 mm is used as the cutoff value. This could be minimized by increasing the cutoff to 10 mm. CONCLUSION: The 2-step approach (initial testing of all cases with TST and confirmation of only those positive in TST by testing with QFT-IT) will be economical and help in treating LTBI cases in lower middle income countries like India.

Comparative study of Smear Microscopy, Rapid Slide Culture, and Lowenstein - Jensen culture in cases of pulmonary tuberculosis in a tertiary care hospital.

BACKGROUND: Tuberculosis (TB), a dreadful disease known to mankind continues to be a problem in a developing country like India. The incidence of people getting infected with TB is on the rise due to compounding factors like coinfection with the human immunodefiency virus and multidrug-resistant strains. There is a definitive need for early diagnosis and treatment of TB to curb transmission of the infection. Direct smear microscopy, though cheap and rapid, lacks sensitivity. Isolation of Mycobacterium tuberculosis in culture requires a long time, because of which there is a need for a rapid method which has good sensitivity and specificity for the detection of M. tuberculosis. The present study was undertaken to determine the test which diagnoses TB rapidly and to compare the sensitivity of smear microscopy, concentration method, rapid slide culture, and Lowenstein - Jensen (LJ) culture. MATERIALS AND METHODS: Sputum samples of 200 patients were subjected to direct smear and concentration by modified Petroff's method. The concentrated sputum was also taken for slide culture using human blood medium and inoculated on LJ media. RESULTS: LJ culture was positive in 47 (23.5%) cases, of which three were nontubercular mycobacteria. Using LJ culture as the standard method, the sensitivity of direct smear, concentration method, and rapid slide culture method was 68, 83, and 89%, respectively, and specificity was 100% in all the three tests. CONCLUSION: Rapid slide culture showed good sensitivity which was comparable to and next in efficacy to LJ culture and this technique can be adopted in the Revised National Tuberculosis Control Program (RNTCP) as it is a rapid, cheap, sensitive, and specific method.