An evaluation of Universal Sample Processing method under Revised National Tuberculosis Control Programme set up for the diagnosis of pulmonary tuberculosis

Context: The main stay in the management of tuberculosis is its early diagnosis and treatment. Aim: To evaluate the utility of Universal Sample Processing (USP) method, claimed to be more sensitive than direct smear microscopy. Materials and Methods: Sputum samples from 1000 patients with history of cough for more than two weeks, visiting the two RNTCP centers between November 2011 and November 2012, were subjected to direct Ziehl–Neelsen staining and staining after USP method. To find out if there was any difference in the time taken to detect Acid Fast Bacilli (AFB) between the methods, the smears were screened by two trained RNTCP technicians. Sputum samples positive for AFB in the USP method were put up for culture on Lowenstein–Jensen medium to evaluate the suitability of USP method as a pre-treatment procedure before culture. The growth was identified as Mycobacterium tuberculosis (MTB) by the Niacin test. Results: Ninety four samples were positive for AFB by both methods. The USP method did not detect more positives among those which were found negative by direct microscopy. There was no significant difference in the time taken to detect AFB between the methods. Among the 94 smear positive samples subjected to USP method as a pre-treatment procedure, only 40 (42.5%) samples yielded growth of MTB. Conclusions: USP technique did not offer additional advantage over direct microscopy for detection of AFB to diagnose pulmonary tuberculosis. As a pre-treatment procedure, USP method yielded low mycobacterial growth even from those samples positive for AFB by microscopy, making it unsuitable for culture of MTB.