Same-day Smear Method Compared with Conventional Sputum Method for Diagnosing Pulmonary Tuberculosis

摘要

Background Patient compliance with the two-day Revised National Tuberculosis Control Programme’s (RNTCP) diagnostic process for pulmonary tuberculosis (TB) is poor in high case load settings, with a high dropout rate observed on the second day. Hence, the World Health Organization (WHO) has recommended the same-day (spot-spot) sputum test for high-burden TB countries to help reduce diagnostic dropouts. This study addresses the paucity of comparative data on the accuracy and agreement of the two methods, while the WHO recommendations are yet to be implemented by the RNTCP. The objective of this study was to assess and compare the smear positivity rates of the same-day and conventional sputum examination methods for the diagnosis of sputum smear-positive pulmonary TB. Methodology We conducted a cross-sectional, analytical, nonrandomized comparative study on presumptive TB patients attending a designated microscopy center in a tertiary care hospital. Three sputum samples were collected: a first spot, a second spot (one hour after the first spot), and an early morning sample taken on the following day. The first and the second spot samples taken one hour apart were included for microscopic analysis. The conventional (i.e., two-day sputum) method used the first spot and the early morning sputum sample taken on the following day. A positive result from any one of the three sputum samples was recorded as a proven TB case. We then compared the results of the smear microscopy obtained by the two methods. Results The same-day sputum microscopic method diagnosed 181 out of a total 189 TB cases. The conventional method diagnosed 188 cases. Thus, same-day sputum microscopy missed eight cases, whereas the conventional method missed only one case. The sputum positivity rate was 18.8% in the same-day sputum microscopy samples and 19.5% in the conventional method samples. The incremental yield of the second sputum sample in the same-day (second spot) sample was five cases (2.7%). In the conventional method (early morning sample), the yield was 12 cases (6.3%). The sensitivity of the same-day microscopy and conventional methods were 95.76% and 99.5%, respectively. Conclusion The conventional method of diagnosing sputum-positive pulmonary TB had more sensitivity compared to the same-day sputum microscopy approach.