Comparison of Fine Needle Aspiration Cytology, Ziehl-Neelsen Staining and GeneXpert Methods in Suspected Cases of Tubercular Lymphadenopathy

Abstract

Introduction: The Extrapulmonary Tuberculosis (EPTB) is challenging due to the pauci-bacillary nature of the disease and limited tests available for early diagnosis. It is the most common extrapulmonary manifestation of tuberculosis. The samples from extrapulmonary infection will have low bacterial count as compared with sputum specimens. It is also necessary to rule out other causes of granulomatous inflammation on Fine Needle Aspiration Cytology (FNAC) and confirmation by Ziehl Neelsen (ZN) stain and Cartridge Based Nucleic Acid Amplification Test (CBNAAT). In December 2010, World Health Organisation (WHO) recommended GeneXpert/CBNAAT to be used as the initial diagnostic test in suspected EPTB cases. Aim: To compare FNAC and ZN stain with CBNAAT in the diagnosis of suspected tubercular lymphadenopathy in a tertiary care centre and to know the importance of CBNAAT in the modern era. Materials and Methods: This was a hospital based prospective study carried out over a period of 12 months (July 2019 to June 2020) in the Department of Pathology and Microbiology, ESIC Medical College. All presumptive cases of tubercular lymphadenopathy and purulent aspirates from the lymph nodes of various sites were included in the study. Smears were made after FNA and stained with Haematoxylin and Eosin (H&E) stain and ZN stain and sample was also processed for CBNAAT in all cases of lymphadenopathy. Statistics were done using SPSS software version 20.00. Results: The total number of cases with presumptive tubercular lymphadenitis was 119. Majority of the aspirates are from jugular lymph nodal and cervical swellings 77 (64.7%) out of 119. FNAC has detected tuberculosis in 20 (16.8%) cases and ZN stain detected Acid Fast Bacilli (AFB) in 6 (5%) cases. CBNAAT has detected 28 (23.5%) cases, among them 15 (12.6%) cases which were not detected by FNAC. Diagnostic Performance of CBNAAT versus FNAC 28 out of 119 showed sensitivity, specificity, negative predictive value and positive predictive value 80%, 85.8%, 65% and 45.5%. Conclusion: The CBNAAT can be added with FNAC to get more specific results. CBNAAT is less sensitive for blood stained samples than purulent samples and hence FNAC still remains as the cheapest and first line test to diagnose in cases suspected of tubercular lymphadenoapathy.