Analysis of the Diagnostic Yield of Nucleic Acid Amplification Tests in Immunocompetent Patients with Tuberculous Cervical Lymphadenitis

Background: Tuberculous lymphadenitis is the most prevalent form of extrapulmonary tuberculosis (TB), accounting for approximately 30-40% of such cases. Nucleic acid amplification tests (NAATs), such as TrueNAT, offer a highly sensitive and rapid diagnostic method for tuberculous cervical lymphadenopathy, including the detection of rifampicin resistance in positive cases. Objectives: 1) To assess the diagnostic effectiveness of TrueNAT in identifying Mycobacterium tuberculosis in fine -needle aspirate (FNA) samples from cervical lymph nodes, compared to Ziehl -Neelsen (ZN) staining. 2) To evaluate the diagnostic yield of TrueNAT by comparing it with cytological findings from FNA samples of cervical lymph nodes and with necrotic findings in these nodes observed via ultrasonography (USG) of the neck. Materials and Methods: This prospective study included 50 patients from July to December 2023. Demographic data and clinical histories were collected. FNA samples underwent TrueNAT testing, cytological analysis, and ZN staining. USG of the neck was performed to detect necrosis in the cervical lymph nodes. Results: The TrueNAT test showed a positivity rate of 70%. Its sensitivity and specificity were evaluated against cytology results, acid -fast bacilli (AFB) detection on ZN staining, and necrotic findings in cervical lymph nodes via USG. The sensitivity and specificity ofTrueNAT were 80.49% and 77.78%, respectively, when compared with FNA cytology showing necrosis; 17.14% and 93.33%, respectively, with AFB positivity on ZN staining; and 74.29% and 33.33%, respectively, with lymph node necrosis observed on USG.Conclusion: The TrueNAT assay is recommended as an adjunctive test to conventional cytological examination of FNA samples from lymph nodes for the rapid diagnosis of tuberculosis, along with simultaneous detection of rifampicin resistance.