Utility of Fine Needle Aspiration Cytology (FNAC) in the diagnosis of tuberculous lymphadenitis compared to GeneXpert in a tertiary health care center in Northern Odisha, India

Abstract

BackgroundDiagnosis of extrapulmonary tuberculosis including tuberculous lymphadenitis (TBLN) is challenging because of its atypical clinical presentation, paucibacillary nature of mycobacteria at the infected sites, variation in sensitivity of a test to specimens collected by different methods and from different infected tissues. MethodsIn the present study, suspected individuals for lymph node tuberculosis irrespective of age were enrolled prospectively and specimens were collected aseptically by fine needle aspiration (FNA). After the implementation of exclusion criteria, FNA specimens from a total of 278 cases of suspected TBLN were evaluated for cytomorphology (FNAC), presence of acid-fast bacillus (AFB) in smear microscopy and specific detection of mycobacterial DNA in cartridge-based nucleic acid amplification test (CBNAAT). ResultsThe results showed high prevalence of Type II (59.71%), followed by Type I (34.53%) and Type III (5.75%) pattern in FNAC. Non-type II patterns were significantly high in regions outside of the head and neck region (P = 0.031; OR = 2.125) and had an increasing trend of their occurrences with progression of age. The most affected age group was between 16 and 30 years with female preponderance documented in individuals below 45 years, whereas male preponderance was observed in higher age group patients, majority of whom had infected lymph nodes outside of HAN region (P = 0.063, OR = 1.998). The results also showed high sensitivity of CBNAAT (83.04%) method followed by FNAC (72.17%) with AFB smear exhibiting the disappointing results (sensitivity of 10.86%) compared to the CRS. High percentage of positivity was observed in Type III (AFB:25% vs CBNAAT: 100%) followed by Type II (AFB:10.2 vs CBNAAT: 76.5), while low detection was observed from samples with Type I (AFB:4.2 vs CBNAAT: 50). Interestingly, CBNAAT detection of TB was shown to be unaffected by gender, age and site of infection. ConclusionThe study suggests a possible contributary role of age and gender for cytomorphological pattern distribution of TBLN at various body parts. Although FNAC detected TB in 77.1% of cases which were identified positive by CBNAAT and/or AFB, it is being solely based on cytomorphology cannot be used alone as a reliable diagnostic method for TBLN detection. Further, the negative results in CBNAAT for FNAC positive cases may not necessarily be non-TB cases and must be evaluated by other diagnostic modalities. We recommend for both cytomorphological investigation and CBNNAT for the fine needle aspirates from suspected TBLN and subsequent treatment to reduce the disease burden.