Novel approach for improving sensitivity of microscopic detection of acid-fast bacilli (AFB) by use of the ReaSLR method.

The ReaSLR methodology developed for sputum processing is a novel, low-cost, and simple technique that has improved the sensitivity of smear microscopy for the diagnosis of tuberculosis (TB). Sample processing consists of rapid liquefaction of the sputum specimen with the ReaSLR reagent, followed by syringe filtration, concentration by centrifugation, and use of the sediment for smear microscopy. The performance of the ReaSLR kit was evaluated on 150 sputum samples and was compared with that of the modified Petroff method for sputum decontamination and concentration. Ziehl-Neelsen staining was performed for smear microscopy after processing by these two techniques; simultaneously, culture on Lowenstein-Jensen (LJ) medium was done to evaluate the two methods. The efficiency of smear microscopy was 18/150 (12%) with the modified Petroff method compared to 47/150 (31.33%) with the ReaSLR method, and this difference was statistically significant (P < 0.001). The ReaSLR method for smear microscopy demonstrated a sensitivity and specificity of 90.47% and 91.6%, respectively, whereas the modified Petroff method showed a sensitivity and specificity of 40.47% and 99.07%, respectively, compared to those of culture, which was used as the gold standard. With the newer ReaSLR method, the kappa coefficient (κ) was 0.8, which implies an excellent positive agreement. The ReaSLR method was found to be more sensitive than the conventional method for sputum smear microscopy. The newer ReaSLR method holds promise for adoption in TB control programs across the globe, as it was found suitable for the laboratory diagnosis of pulmonary TB. Further large-scale studies are needed to evaluate other aspects of this method.