Rapid Mycobacterium tuberculosis DNA Detection on Fine Needle Aspirates from Extra Pulmonary Lymph Nodes

To evaluate the diagnostic efficacy of two rapid methods i.e. Mycobacterium tuberculosis (MTB) Polymerase Chain Reaction (PCR) on Fine Needle Aspiration (FNA) samples by comparing with cytology of respective site sample.

Cross-sectional comparative study.

Department of Microbiology, Armed Forces Institute of Pathology (AFIP), Rawalpindi, Pakistan, from July 2010 through November 2013.

A total of 105 extra pulmonary lymph nodes aspirates obtained through fine needle aspiration were processed. Cytology and PCR were done on each specimen. Cytology was taken as gold standard.

Out of the total 105 samples, 71 (67.6%) were positive for the MTB PCR while 34 (32.4%) showed negative status. According to FNA cytology (FNAC) results, 72 (68.6%) cases were positive for the disease while 33 (31.4%) were negative. Sensitivity of PCR was 90.3%, specificity 81.8%, positive predictive value (PPV) 91.5%, negative predictive value (NPV) 79.4%, with diagnostic accuracy of 87.6%. Area under the curve was 0.860 (p < 0.001).

PCR is a sensitive tool for detection of MTB on FNA samples from EPTB cases. The results are available within few hours which is helpful for the clinicians to initiate therapy.