Significance of non‐granulomatous cytomorphology on fine needle aspirate in lymphadenitis cases classified as tuberculous by using a composite reference standard

Abstract

AbstractBackgroundFine needle aspiration cytology (FNAC) is established as a first line investigation for tuberculous lymphadenitis (TBLA). We aimed to describe the various cytomorphologic features of tuberculosis (TB) on FNAC and their contribution in the diagnostic decision‐making in suspected TBLA cases.MethodsPatients with presumptive TBLA were prospectively enrolled (n = 266) and subjected to routine diagnostic work‐up for TB, including FNAC samples, and followed until the end of treatment. Patients were categorized as TB or non‐TB cases based on a composite reference standard of which the various cytomorphologic patterns were compared. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy was calculated using cross‐tabulation.ResultsFifty‐six patients were categorized as bacteriologically confirmed TB, 102 as clinically confirmed TB and 108 as non‐TB. The most common cytomorphologic pattern among TB cases (59%) was granulomatous inflammation with necrosis, however, about one‐third of tuberculous lymphadenitis patients presented with non‐granulomatous inflammation, with 21% showing only necrosis and 13% presenting with a reactive pattern. The overall sensitivity and specificity of FNAC was 85% and 66%, respectively.ConclusionsWe found that about one‐third of TBLA patients presented without granulomas on FNA, highlighting the importance of considering TB in a wide spectrum of cytomorphology in a high TB burden setting. Our study supports the use of FNAC as a first‐line investigation tool for diagnosing TBLA in a low‐resource setting due to its relative simplicity and good sensitivity. However, the low specificity of FNAC, emphasizes the need for a second‐tier confirmatory test with improved specificity.