Smear microscopy as surrogate for culture during follow up of pulmonary MDR-TB patients on DOTS plus treatment.

ABSTRACT

Background: DOTS Plus site at LRS Institute, New Delhi, covering 1.8 million population. Aims: To ascertain if sputum smear could be used as a surrogate for culture during intensive phase of treatment of MDRTB patients thereby enabling early shift from intensive phase to continuation phase, reducing the need for frequent cultures and saving time and cost in their management. Methods: The study is a retrospective analysis of 138 MDR-TB patients on DOTS Plus treatment whose sputum samples were simultaneously subjected to smear microscopy and culture, monthly during Intensive Phase and once in two months during Continuation Phase. Sputum results in the treatment card were supplemented from laboratory register, if required, and analyzed. Predictive values, sensitivity and specificity of smear were compared with culture results. Results: The Negative Predictive Value (NPV) of smear was high from the 3rd month onwards (above 91%), at four months 98% or more and approached 100% from eight months onwards. The specificity of smear test gradually increased during treatment and from five months onwards, it was above 90%. Conclusions: Considerable correlation was observed between sputum smear and culture during follow up of DOTS Plus treatment in the Intensive Phase. Accordingly, sputum smears can be recommended instead of culture.