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Indian Journal of Medical Microbiology
Medknow Publications on behalf of Indian Association of Medical Microbiology
ISSN: 0255-0857 EISSN: 1998-3646
Vol. 27, Num. 3, 2009, pp. 277-278

Indian Journal of Medical Microbiology, Vol. 27, No. 3, July-September, 2009, pp. 277-278

Correspondence

Comparision of performance characteristics of automated PCR systems with culture for detection of MTB complex from clinical samples in Central India

Desikan P, De S, Mishra P, Jain A, Panwalkar N, Verma M, Maudar KK

Department of Microbiology, Bhopal Memorial Hospital and Research Centre, Raisen Bypass Road, Karond, Bhopal, Madhya Pradesh, 462 038
Correspondence Address:Department of Microbiology, Bhopal Memorial Hospital and Research Centre, Raisen Bypass Road, Karond, Bhopal, Madhya Pradesh, 462 038
prabhadesikan@yahoo.com

Date of Submission: 13-Aug-2008
Date of Acceptance: 17-Sep-2009

Code Number: mb09082

PMID: 19584519
DOI: 10.4103/0255-0857.53220

Dear Editor,

Most published studies on performance characteristics of the COBAS AMPLICOR (CA) system and Real Time PCR (RT-PCR) for detection of Mycobacterium tuberculosis have been carried out in countries other than India. [1] Strains of M. tuberculosis are known to vary in their genomic structure between geographical regions. Performance characteristics of these tests have not been determined on locally prevalent strains in Central India.

This study is an initial retrospective examination of the performance characteristics of the COBAS AMPLICOR MTB test and RT-PCR on 66 clinical samples in Central India [Table - 1]. With culture as the gold standard, the sensitivity of CA was 88.88% and specificity, 88.46%. Positive predictive and negative predictive values were 72.72% and 95.83%, respectively. These results are at variance with those reported earlier. [2],[3],[4] The overall sensitivity of the RT-PCR was found to be 66.66% and overall specificity was found to be 87.5%. Internal controls were inhibited while testing 12 specimens by RT-PCR and thus gave non-reactive results. This could explain the low sensitivity, which is lower than that reported earlier. [5] Overall positive predictive value and negative predictive values for RT-PCR were observed to be 82.35% and 75%, respectively.

This observed variation may be due to a genotypic difference between the locally circulating Mycobacterial strains and strains tested in previous studies. A change in the geographical region, may, therefore, alter the reported performance characteristics of some commercially available PCR tests. Further studies, with larger sample sizes, are needed to confirm this.

References

1.Fegou E, Jelastopulu, Sevdali M, Anastassiou ED, Dimitracopoulos G, Spiliopoulou I. Sensitivity of the Cobas Amplicor system for detection of Mycobacterium tuberculosis in respiratory and extrapulmonary specimens. Clin Microbiol Infect 2005;11:593-96.   Back to cited text no. 1    
2.Bodmer T, Gurtner A, Scholkmann M, Matter L. Evaluation of the COBAS AMPLICOR MTB system. J. Clin Microbiol 1997;35:1604-5.  Back to cited text no. 2    
3.Ninet B, Rohner P, Metral C, Auckenthaler R. Assessment of use of the COBAS AMPLICOR system with BACTEC 12B Cultures for Rapid Detection of Frequently Identified Mycobacteria . J. Clin Microbiol 1999;37:782-4.  Back to cited text no. 3    
4.Eing BR, Becker A, Sohns A, and Ringlemann R. Comparison of Roche Cobas Amplicor Mycobacterium tuberculosis Assay with In-House PCR and Culture for Detection of M. tuberculosis. J. Clin Microbiol 1998;36:2023-9.  Back to cited text no. 4    
5.Shrestha NK, Tuohy MJ, Hall GS, Reischl U, Gordon SM, Propcop GW. Detection and Differentiation of Mycobacterium tuberculosis and Nontuberculous Mycobacterial Isolates by Real-Time PCR. J. Clin Microbiol 2003;41:5121-6.  Back to cited text no. 5    

Copyright 2009 - Indian Journal of Medical Microbiology

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