Evaluating suspected cases of tubercular lymphadenopathy: A comparative analysis of fine needle aspiration cytology, CBNAAT and AFB screening with Ziehl-Neelsen staining

Abstract

Introduction: Tubercular lymphadenopathy poses a diagnostic challenge due to its varied clinical presentations and overlapping features with other diseases. The incidence of tuberculosis in India has dramatically increased and contributing to it is Human Immunodeficiency Virus (HIV). Preliminary findings suggest that FNAC provides rapid cytological insights but may lack specificity. AFB screening using Ziehl-Neelsen staining demonstrates high specificity but is limited by sensitivity, especially in paucibacillary cases. CBNAAT emerges as a promising molecular diagnostic tool with superior sensitivity and specificity, potentially reducing the time to diagnosis. In December 2010, the World Health Organization (WHO) endorsed the use of GeneXpert/CBNAAT as the primary diagnostic test for suspected extrapulmonary tuberculosis (EPTB) cases. Aims and Objective: To assess the diagnostic effectiveness of three commonly used techniques—Fine Needle Aspiration Cytology (FNAC), Acid-Fast Bacilli (AFB) screening with Ziehl-Neelsen staining, and the Cartridge-Based Nucleic Acid Amplification Test (CBNAAT)—in cases where tubercular lymphadenopathy is suspected. Materials and Methods: This prospective study was conducted within a hospital setting over a 12-month period, spanning from October 2022 to September 2023. It encompassed all individuals presenting as presumptive cases of tubercular lymphadenopathy and those with purulent aspirates from lymph nodes at various sites. Following fine needle aspiration (FNA), smears were prepared and stained using Haematoxylin and Eosin (H&E), Papanicolaou (PAP), May-Grünwald-Giemsa (MGG), and Ziehl-Neelsen (ZN) techniques. Additionally, samples from all lymphadenopathy cases underwent processing for Cartridge-Based Nucleic Acid Amplification Test (CBNAAT). Statistical analyses were performed using SPSS software version 20.00. Results: Total number of suspected cases were 107. Majority of aspirates were from cervical region (89.7%) i.e 96 cases from 107. Fnac diagnosis of Tubercular Lymphadenitis was given in 12 cases (11.2%). ZN Stain was positive in 12 cases (11.2%). CBNAAT detected tuberculosis in 32 cases (29.9%), among them 4 cases (3.7%) not detected by FNAC. Conclusion: While FNA remains the most cost-effective test for diagnosing TB, CBNAAT plays a crucial role in the diagnosis of extrapulmonary tuberculosis (EPTB) in cases featuring granulomatous lymphadenitis and purulent aspirates. Furthermore, CBNAAT provides rapid detection of rifampicin-resistant M. tuberculosis strains, presenting an additional advantage in the diagnostic process.