Are we justified in treating for multidrug-resistant tuberculosis based on positive follow-up smear results?

Kumar, R.S.; Kumar, A.M.V.; Claassens, M.; Banurekha, V.V.; Gomathy, S.; Venkatesan, P.; Swaminathan, S.

International Journal of Tuberculosis and Lung Disease; 2014; 18; 449-453.

Summary: Setting: National Institute for Research in Tuberculosis , India .

Objective: To assess, among new culture-confirmed smear-positive pulmonary tuberculosis (TB) patients, the proportion of follow-up smear-positives that were culture-negative (S+C-) by month of follow-up examination, human immunodeficiency virus (HIV) status, pre-treatment drug susceptibility status and smear grading.

Design: We extracted follow-up smear (fluorescence microscopy) and culture (Lowenstein-Jensen) results of patients enrolled in clinical trials from January 2000 to August 2012 and treated with the WHO Category I regimen (2EHRZ 3 /4HR 3 ).

Results : Of 520 patients, including 176 who were HIV-infected, respectively 199, 81, 47 and 43 were smear-positive at months 2, 4, 5 and 6; of these, respectively 138 (69%), 62 (75%), 32 (68%) and 27 (63%) were culture-negative. The S+C- phenomenon was more pronounced among ‘1+positive' patients than in 2+ or 3+ positive patients and in ‘pan-susceptible' patients than in those with any resistance, and did not vary by HIV status.

Conclusion: Nearly two thirds of patients with follow-up smears positive at months 5 and 6 were culture-negative. Starting multidrug-resistant TB (MDR-TB) treatment empirically based on smear results, even in resource-limited settings, is incorrect and can have hazardous consequences. There is an urgent need to revisit the WHO recommendation concerning empirical MDR-TB treatment.

Keywords : Empiric MDR-TB treatment; S+C-phenomenon; sputum smear; sputum culture; pulmonary tuberculosis

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