Integrating Cartridge-based Nucleic Acid Amplification Test and Cytology for Enhanced Diagnosis of Lymph Node Tuberculosis: A Retrospective Study

Introduction: Tuberculosis (TB), particularly its extrapulmonary form (EPTB), remains a major public health concern in developing countries like India.Lymph node tuberculosis (tuberculous lymphadenitis) is the most prevalent form of EPTB, representing about 35% of cases.Due to the low bacterial load in affected tissues and challenges in specimen collection, its diagnosis is often delayed or missed.While Fine Needle Aspiration Cytology (FNAC) is commonly used for morphological evaluation, the Index TB guidelines recommend the addition of cartridge-based nucleic acid amplification test (CBNAAT) for improved diagnostic accuracy. Aims and objectives:The study aimed to assess the diagnostic correlation between cytology and CBNAAT findings in patients suspected of having tuberculous lymphadenitis and to detect cases with rifampicin-resistant TB. Materials and methods: This retrospective observational study was conducted at the Departments of Respiratory Medicine and Pathology, Government Medical College, Bhavnagar, Gujarat, India from 1 June 2023 to 30 May 2024.A total of 62 patients aged 18-65 years presenting with palpable cervical lymphadenopathy and not on anti-TB treatment were included.Lymph node aspirates were subjected to both cytology and CBNAAT analysis.Data were compiled in Microsoft Excel and statistically analyzed using IBM SPSS version 26, with results expressed as frequencies and percentages.Results: Among the 62 cases, 32 (51.62%) were female and 30 (48.38%) were male.Cytology indicated tuberculous features in 25 cases (40%), while CBNAAT detected Mycobacterium tuberculosis in 17 cases (27%), with two showing rifampicin resistance.Ten cases (16%) were positive by both methods, and 30 (48%) were negative in both.Discordant results were found in 22 cases-15 (24%) were CBNAAT-negative but cytologypositive, and 7 (12%) were CBNAAT-positive but cytology-negative. Conclusion:The findings affirm that neither cytology nor CBNAAT alone is sufficient for accurate diagnosis of tuberculous lymphadenitis.While FNAC is accessible and cost-effective, it lacks specificity.Cartridge-based nucleic acid amplification test though highly specific and capable of detecting drug resistance, may yield false negatives in paucibacillary conditions.A combined diagnostic approach using both modalities enhances diagnostic accuracy and enables timely and appropriate treatment.Future research should focus on improving CBNAAT sensitivity and integrating newer molecular diagnostics for broader clinical application, especially in resource-limited settings.