Introduction: Diagnosis of Extrapulmonary TB (EPTB) remains a challenge as the number of Mycobacterium tuberculosis (MTB) bacilli present in tissues and pus samples from various sites of disease are often low & non-uniformly distributed. Molecular diagnostic methods like GeneXpert or Cartridge-based nucleic acid amplification test (CBNAAT) seems to hold the key to future of better and efficient diagnosis of Extrapulmonary Tuberculosis (EPTB) in pus and tissue samples as it simultaneously detects M. tuberculosis and Rifampicin resistance in samples.

Material & Methods : A Retrospective cross sectional study was carried out in the Department of Microbiology. This study includes pus and tissue samples from November 2021 to December 2022 – 14 months. All pus and tissue samples were subjected to aerobic culture, simultaneously Gram stain, ZN stain, Modified ZN stain, KOH mount were performed among them. All samples that met the inclusion criteria which were sterile and smear negative (Gram stain, ZN stain, Modified ZN, KOH mount) were subjected to clinical evaluation. In these cases, detailed clinical history for TB were taken and samples were subjected to GeneXpert. Later on data were analysed on the basis of clinically suspected and clinically not suspected for TB.

Inclusion criteria: Frank Pus sample > 3 ml, Tissue minimum 1 gm

Exclusion criteria: Blood-stained Pus, Pus samples < 3 ml, Pus swab, Tissue received in Formalin, Clinical history not available

Results: Total 387 samples (360 pus, 27 tissue) received for aerobic culture. Among them 198 samples (181 pus, 17 tissue) were aerobically sterile and smear negative (Gram stain, Zn stain, Modified ZN, KOH mount). Out of 181 pus samples, 47 samples (13.05%) met the inclusion criteria and were subjected to Gene-Xpert. Among these 15 positive samples, 11 samples (23.40%) were clinically suspected & 4 samples (8.51%) clinically not suspected were detected of M. Tuberculosis. Among 27 tissue samples, 17 sterile and smear negative samples were subjected to Gene-Xpert, among them only 2(11.76%) clinically not suspected samples of Tissue were detected for M. Tuberculosis.

Conclusion: Diagnosis of EPTB is very important as pus and tissue are regarded as precious samples which cannot be repeatedly retrieved. Our data suggest use of GeneXpert for diagnosis of EPTB in smear negative, aerobically sterile pus & tissue samples.