Comparative Analysis Of Cytomorphological Patterns And CBNAAT Results In Diagnosing Extra-Pulmonary Tuberculosis: A Retrospective Study

Background: Extra-pulmonary tuberculosis (EPTB) offers diagnostic problems due to its diverse clinical presentations and low bacterial burden.While the Cartridge-Based Nucleic Acid Amplification Test (CBNAAT) provides high diagnostic accuracy and quick findings, Fine Needle Aspiration Cytology (FNAC) remains a low-cost, non-invasive diagnostic approach.The purpose of this study is to evaluate cytomorphological patterns in FNAC of CBNAAT-positive EPTB cases and compare them to CBNAAT results.Methods: This retrospective analysis was carried out in Government Medical College Karur from June 2021 to May 2024.We collected CBNAAT-positive EPTB cases and examined their FNAC slides.Clinical information, such as age, gender, and clinical presentation, were obtained.FNAC slides were examined for cytomorphological features including granuloma, caseous necrosis, multinucleated giant cells, and fibroblasts.CBNAAT results were divided into four categories: very low, low, medium, and high bacterial burdens.The sensitivity of cytomorphological patterns was also assessed.Results: Out of 34 CBNAAT-positive EPTB cases, the majority were 51-60 years old, with a small female predominance.Lymph nodes were the most prevalent site (61.7%).CBNAAT discovered MTB at four levels: very low (41.1%),low (35.3%),medium (20.5%), and high (2.9%), with one case demonstrating Rifampicin resistance.Cytomorphological patterns revealed granuloma with caseous necrosis in 44.1% of patients, with lymph nodes being more sensitive (65%) to granuloma with caseation.High MTB values frequently lacked identifiable cytomorphological characteristics, implying immunosuppression.Conclusion: FNAC is a useful first diagnostic technique for EPTB, especially in lymph nodes, where it is highly sensitive when paired with caseation.However, the presence of a high MTB load in the absence of normal cytomorphological traits suggests that more research into immunosuppressive consequences is needed.CBNAAT is critical for the correct and timely diagnosis of EPTB.