Comparison of modified Petroff′s and N-acetyl-L-cysteine-sodium hydroxide methods for sputum decontamination in tertiary care hospital in India

Background : Tuberculosis is the second leading cause of death worldwide, killing nearly two million people each year. Sputum decontamination with N-acetyl-L-cysteine-sodium hydroxide (NALC-NaOH) is expected to improve detection of Mycobacterium tuberculosis (M. tb) by culture better than that with modified Petroff′s; which is widely used in laboratories. In this study, sputum samples collected from suspected cases of pulmonary tuberculosis (TB) were cultured directly on Lowenstein-Jensen (LJ) medium and after decontamination by both the methods and the results of smear and culture positivity were evaluated to assess whether the NALC-NaOH treatment method improves smear and culture. Materials and Methods : For each decontamination method, 30 samples were obtained from suspected cases of Pulmonary TB, from Pad. Dr. D.Y. Patil Medical College and Hospital. Two sputum samples from each patient were collected on day 1 and 2. These samples then underwent decontamination process by performing the 4% NaOH, NALC-2% NaOH treatment methods and direct inoculation. After each process a smear was made and culture was done on LJ medium. Results: The modified Petroff′s and NALC-NaOH treatment methods did not significantly affect the AFB smear positivity of the sputum samples (66% and 72.3%, respectively). (However, the culture positivity for M. tb on LJ medium was significantly different by the three processes. With NALC-NaOH and modified Petroff′s it was 63% and 46%, respectively, while with direct culture it was 23%. Conclusion: NALC-NaOH treatment is better than modified Petroff′s treatment for the detection of M. tb by culture. However, AFB microscopy does not seem to be significantly different by either process