Incremental yield in sputum smear positivity by examining a second early morning sputum specimen in follow-up patients on DOTS: 7 year analysis of RNTCP laboratory register.

Background: Patients receiving DOTS undergo periodic follow-up sputum examination, which aids in monitoring response to treatment. Continued or new smear positivity at follow up examination entails extension of intensive phase or change in treatment category and the need for culture and drug susceptibility test.

Setting: Tuberculosis microscopy centre at a tertiary care teaching hospital, Mumbai, India.

Objective: To determine the incremental yield in sputum smear positivity by examining a second early morning sputum specimen in follow-up patients on DOTS.

Design: Retrospective analysis of follow up sputum microscopy results recorded in tuberculosis laboratory register for the period 2002-2008.

Results: During the study period, 5015 follow-up patients submitted two early morning sputum specimens, of which 501(9.99%) patients were detected to be smear-positive. Out of smear positive patients under study, 324 patients had both specimens positive, 79 patients had only first specimen positive and 98 patients had only second specimen positive. The incremental yield was 1.95% of total and 19.5% of smear positives.

Conclusion: Discordant smears were present in nearly a third of patients detected smear positive during follow-up. More than half of these patients were detected only by examining second specimen. The incremental yield by examining the second early morning specimen was 1.95% of total and 19.5% of smear positive specimens. It is important to detect each possible smear positive follow-up patient as they are likely to benefit from altered treatment. The inclusion of a second early morning sputum specimen examination is essential to maximize their detection.