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Indian Journal of Medical Microbiology, Vol. 29, No. 4, October-December, 2011, pp. 445-446 Correspondence Need to establish importance of polymerase chain reaction for tuberculosis in smear as well as culture negative non-respiratory samples V Gupta, N Singla, R Garg, N Gulati, H Rani, J Chander Department of Microbiology, Government Medical College Hospital, Chandigarh, India Date of Submission: 18-Aug-2011 Code Number: mb11112 PMID: 22120818 Dear Editor, The diagnosis of extra pulmonary tuberculosis (EPTB) immediately and conclusively is difficult as it involves deeply located inaccessible anatomical sites and requires invasive procedures to obtain the samples which are often paucibacillary. [1] Therefore, clinicians often go for empirical therapy. But emergence of extensively drug-resistant tubercular organisms has necessitated the need for a quick and rapid diagnosis. So, polymerase chain reaction (PCR) for diagnosis has attracted considerable interest. [2] This retrospective study (January 2006 to June 2010) is of 98 non-respiratory samples for PCR for M. tuberculosis. Out of 98, the results of 86 samples are depicted in [Table - 1]. Twelve other samples including gastric aspirate (4), cul de centesis fluid (2), ovarian cyst fluid (2), urine (2) and gastric biopsy (2) were negative by both conventional and molecular methods. Diagnosing tubercular infection with conviction varies with its clinical presentation and also depends upon the quality of sample. In all EPTB cases, molecular methods like PCR may clinch the diagnosis by being rapid, sensitive and specific helping in early diagnosis. [2],[3],[4],[5] Practically in routine microbiology laboratory, it is not feasible to confirm the result of a sample which is positive by PCR alone and thus confusion prevails whether the anti-tubercular treatment should be started in such cases or not. However, if the PCR has been performed under controlled conditions, it should be considered significant. Moreover, in EPTB there are strong chances of conventional techniques being negative, but PCR having a lower limit of detection may be positive. Also, India being an endemic country, there are always higher chances of the patients having TB than not. We are well aware of the limitations in the study. However, we summarize that PCR using more than one primer can be considered useful in diagnosing EPTB cases. No doubt, the disadvantage of over- diagnosis remains but ′benefit of doubt′ should be given to the patient and the advantages of successful observed treatment must be considered to avoid irreversible complications. References
Copyright 2011 - Indian Journal of Medical Microbiology The following images related to this document are available:Photo images[mb11112t1.jpg] |
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