Assessment of possible tuberculous lymphadenopathy by PCR compared to non-molecular methods

Tuberculosis is a major public health problem in India and other developing countries and has formed a lethal partnership with AIDS. It often presents a diagnostic challenge especially when clinical presentation is suggestive but bacteriological proof is lacking. The objective of this study was to compare the various diagnostic techniques in clinically suspected cases of tubercular lymph nodes and to find a suitable, cost-effective but sensitive and specific method for diagnosis. A total of 100 cases were recruited for the study. Fine needle aspiration cytology was done in all cases and the smears prepared were processed for Giemsa, Ziehl-Neelsen's, Kinyoun and Papanicolaou stains. Parts of the aspirated materials were assessed by fluorescent staining, culture and PCR. Seventy-four percent of aspirates were positive by fluorescent stain while only 22% were positive by culture. PCR could be performed in 55 cases, out of which 22 (40%) were positive. When compared to culture, the sensitivity and specificity of PCR were found to be 89.5% and 86.1%, respectively. Fluorescent stain was found to be the most sensitive (81.8%) of the conventional methods but showed poor specificity (28.2%). Interestingly, PCR detected 80% of smear-negative but culture-positive cases.