Molecular biology technique combined with Fine needle aspiration cytology revealing the diagnostic dilemma in tubercular lymphadenitis cases

Abstract

Background: Extra-pulmonary Tuberculosis in the form of tubercular lymphadenitis (TBLN) accounts for 30-40% of Tuberculosis cases. Tuberculosis lymphadenitis is not always associated with the clinical symptoms like fever, cough, weight loss etc which makes its diagnosis difficult. Moreover, conventional investigations like culture and Ziehl Neelsen staining (ZN) used for providing the bacteriological evidence of TBLN have their own limitations. These cases therefore remain undiagnosed and become worse when left untreated. Such cases have potential to spread tuberculosis and thus are problem areas to the public health. We aim to reveal the diagnostic dilemma by molecular biology technique based on real-time Polymerase chain reaction (PCR) with the hypothesis that Real-time PCR performed on lymph node aspirates will be able to diagnose tubercular lymphadenitis cases which lack clinical and bacteriological evidence of tuberculosis on conventional methods. Research problem with aproach Methods & Materials: Cross sectional study: Fifty patients with enlarged lymph node, enrolled in this study were taken for cytological evaluation to Department of Pathology, Jawaharlal Nehru Medical College, Wardha, India. Informed consent was taken. Lymph nodes were subjected to Fine needle aspiration cytology (FNAC); aspirates obtained were used for studying morphology, ZN staining, culture and TaqMan based real time PCR on target insertion sequence IS6110. The results were recorded and data analyzed in Software package for statistical analysis.Inclusion and exclusion criteria and study process Results: Female to male ratio was 1.3:1. Most common site among lymph nodes was cervical in 72%, cases. Morphologically necrotizing granuloma was seen in 20/30 cases diagnosed TBLN on Fine needle aspiration cytology, ZN staining was positive only in 15 cases, culture was positive only in 20 cases and TaqMan based real-time PCR findings were positive in 35 cases. Ten cases missed for TBLN on conventional methods (culture and ZN stain) were diagnosed by FNAC and PCR. Five cases missed for TBLN on FNAC were diagnosed by PCR. Diagnostic accuracy of real-time PCR was found to be 100%. Results Conclusion: A positive real-time PCR finding on aspirates of lymph nodes reveals the diagnostic dilemma in tubercular lymphadenitis cases where there was no clinical suspicion and bacteriological proof was lacking. In addition real time PCR helps to diagnose the cases missed on morphology.