Comparison of Two Sputum Processing Methods for DetectingMycobacterium tuberculosisby Culture and PCR: Universal Sample Processing (USP) and NALC-NaOH Methods

Abstract

Background: The universal sample processing (USP) method has recently been introduced as a simple technique that is applicable to smear microscopy, culture, and polymerase chain reaction (PCR) for the detection of Mycobaterium tuberculosis (MTB). The present study evaluated the utility of the USP meth- od for detecting MTB by culture and PCR, and the results were compared with that of the N-acetyl L-cysteine (NALC)-NaOH (6%) method. Methods: All sputum specimens were digested and decontaminated by both the USP and NALC-NaOH methods, and the processed samples were in- oculated for MTB culture and PCR. Culture was per- formed (252 samples) by using the MGIT system (Becton Dickinson Microbiology Systems, Sparks, Md, USA), and PCR test was conducted (281 sam- ples) by using Amplicor MTB kit (Roche Molecular Systems, Branchburg, N.J., USA). Results: MTB culture positive rates by NALC-NaOH and USP methods were 13.5% (34/252) and 11.9% (30/252), respectively (P>0.05). There were no sig- nificant differences between the two methods for de- tecting MTB by PCR: the MTB PCR sensitivities by USP and NALC-NaOH methods were 77.8% (49/63) and 82.5% (52/63), respectively, and the specificities were 95.9% (209/218) and 96.3% (210/218), re- spectively (P>0.05). Conclusion: There were no significant differences be- tween USP and NALC-NaOH methods of sample processing in enhancing the detection of MTB by culture or PCR. (Korean J Clin Microbiol 2009;12: 67-71)