Precision in practice: Comparative evaluation of cytomorphological findings, acid-fast bacilli staining and cartridge-based nucleic acid amplification test for diagnosing suspected cervical tubercular lymphadenopathy

Abstract

Introduction: India has the highest burden of tuberculosis with an incidence of 2,590,000 in 2021. Extrapulmonary TB constitutes 15-20% of all TB cases with the lymph node being the most common site. Due to its paucibacillary nature, EPTB is a diagnostic and therapeutic challenge.
Objectives: Comparing FNAC with AFB staining and CB-NAAT for diagnosing cervical tubercular lymphadenopathy.
A study was conducted at Dr. B.R. Ambedkar Medical College and Hospital, Bangalore from Oct 2021 to Jan 2023. 102 suspected cases of cervical tubercular lymphadenopathy were included. Smears were made with FNAC aspirates, stained with H&E, PAP, and AFB, and the remaining aspirate was sent for the CB-NAAT test.
Results: In 102 cases, the most affected age group is 21-30 years with more females. Most cases were seen in level V. The 46 cases showed granulomatous lymphadenitis with necrosis. The highest number of CBNAAT and AFB positivity is seen in necrotizing lymphadenitis. CBNAAT showed the most positivity in caseous (87.5%) and the least in blood mixed (35.38%). Overall, CBNAAT showed positivity in 54 cases and AFB showed positivity in 19 cases. CBNAAT demonstrated greater sensitivity (81.97%) than AFB (31.15%) while maintaining high specificity (90.2%) and positive predictive value (92.6%).
Conclusion: CBNAAT is a newer and more sensitive diagnostic test for extrapulmonary tuberculosis as compared to FNAC. It is recommended to use CBNAAT in addition to smear microscopy and cytology in FNAC specimens for early and accurate diagnosis and prompt treatment of EPTB.