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Is universal sample processing methodology better than conventional techniques for detection of tuberculosis?
V Mittal1, F Haider, S Singhal
1Department of Microbiology, Dr. Ram Manohar Lohia Institute of Medical Sciences, Lucknow, Uttar Pradesh, India.
Background:
The identification of infectious cases is a crucial first step for tuberculosis control programmes worldwide. It relies exclusively on the detection of acid-fast bacilli in sputum by smear microscopy. Therefore, there is an urgent and definite need to improve the sensitivity of smear microscopy.
Objective:
The USP method was compared with the two most commonly used conventional methods of smear microscopy namely; direct smear microscopy and the microscopy by modified Petroff's method.
Materials And Methods:
Two samples from each patient were taken from 197 patients of presumptive tuberculosis. One smear was made for direct Ziehl-Neelsen staining and two smears were made after processing by two concentration methods i.e., modified Petroff's and USP solution. LJ media were inoculated for culture after processing by both concentration methods.
Results:
Among 197 cases 93 were culture positive by either method. Out of 93 culture-positive sample, 78.5% were direct smear positive, 89% were 4%NaOH smear positive and 96% were USP smear-positive samples but difference in diagnostic accuracy of USP (96%) and modified Petroff method (93%) is not statistically significant (P>0.01).
Conclusion:
The present study evaluated the smear microscopy by USP method with two conventional methods, direct microscopy and microscopy by modified Petroff's method. The study concludes that although USP method is more sensitive than conventional methods, it is not feasible to include it in diagnosis of early tuberculosis within RNTCP.
