Evaluation of two pretreatment methods for the detection of Mycobacterium tuberculosis in suspected pulmonary tuberculosis.

The objective of the current study was to compare the efficacy of phenol ammonium sulphate (PhAS) and sodium hypochlorite (NaOCl) pretreatment methods for the direct microscopy with the Löwenstein-Jensen (LJ) culture to detect acid fast bacilli (AFB) from pulmonary tuberculosis suspected cases using sputum specimens. To evaluate PhAS and NaOCl methods, sputum specimens (n = 1145) were studied and the performance of each method was compared with LJ media. The, PhAS centrifuged smear and NaOCl centrifuged smear method demonstrated higher sensitivity (71.47% and 77%), specificity (99.61% and 98%), positive predictive value (98.8% and 94.88%) and negative predictive value (88.35% and 90.25%), respectively, when compared to LJ culture. However, the direct AFB smears and PhAS centrifugation method was ineffective to detect few Mycobacterium tuberculosis cases from sputum specimens, particularly in blood tinged specimens with scanty bacilli. Interestingly, NaOCl method could efficiently detect the Mycobacterium tuberculosis cases from blood tinged sputum specimens with scanty bacilli. The current study concluded that NaOCl method could be the most efficient and sensitive method than direct AFB smear and PhAS centrifuged smear method for the direct detection of AFB in suspected cases of pulmonary tuberculosis.