Evaluation of a novel sputum processing ReaSLR methodology for improving sensitivity of smear microscopy in clinical samples.

Background: Early case detection is a crucial step in the control of tuberculosis (TB). Sputum smear microscopy is the primary method of TB diagnosis in developing countries. The modified Petroff's method using sodium hydroxide at concentrations ranging between 2% and 4% to digest the specimen is widely used in developing countries. A novel ReaSLR (ReaMetrix's Sputum Liquefying Reagent) methodology has been proposed as a simple, easy, low-cost, and better alternative to conventional methods for sputum processing. This study was undertaken to evaluate the performance of the ReaSLR method of sputum processing in comparison with that of the modified Petroff's method.

Methods: Early-morning sputum samples were collected. After preparing a direct smear, each sample was divided into two equal halves and processed by both the methods, i.e., modified Petroff's method and ReaSLR method. Direct smears were graded according to Revised National Tuberculosis Control Program grading, and smears prepared after processing by the two different methods were graded according to Center for Disease Control and Prevention grading. Smear microscopy results were compared taking culture results of samples processed by the modified Petroff's method as the gold standard.

Results: The rate of smear positivity with the modified Petroff's method (22.22%) was found to be higher than that with direct smear microscopy (13.56%; p = 0.0002) and the ReaSLR method (17.32%; p = 0.04). The modified Petroff's method was found to be 26.76% more sensitive than direct microscopy and 15.59% more sensitive than the ReaSLR method.

Conclusion: The ReaSLR method was not superior to the modified Petroff's method for smear microscopy. Although this method was more sensitive than the direct method in smear microscopy, the modified Petroff's method performed much better than the ReaSLR method.