Distribution of extrapulmonary tuberculosis in CBNAAT samples received in a tertiary care hospital - A record-based study.

Background: Pulmonary tuberculosis (PTB) accounts for 85% of all reported tuberculosis cases globally. Extrapulmonary involvement can occur in isolation or along with a pulmonary focus as in the case of patients with disseminated tuberculosis (TB). EPTB can occur through hematogenous, lymphatic, or localized bacillary dissemination from a primary source, such as PTB and affects the brain, eye, mouth, tongue, lymph nodes of neck, spine, bones, muscles, skin, pleura, pericardium, gastrointestinal, peritoneum and the genitourinary system as primary and/or disseminated disease. Although pulmonary TB is the most common presentation, EPTB is also an important problem clinically. Cartridge-based nucleic acid amplification (CBNAAT) test has a well-documented role in diagnosing pulmonary tuberculosis.

Aim: To determine the distribution of EPTB in various samples received for CBNAAT testing in our Institution.

Methods: In this retrospective cross-sectional study, data of suspected EPTB patients were retrieved and analyzed from January 2020 to December 2022.

Statistical Analysis: All the statistical analyses were carried out using the Excel spreadsheet and Open-epi version 3.01 platform.

Results: A total number of 1118(n) extrapulmonary samples were processed using GeneXpert MTB/RIF assay. Out of the 1118 received samples, (22%) were positive. Among the 249 positive samples, 55% samples were received from the female patients and 45% samples received from the male patients. We found that most MTB positive samples were from this age group (i.e. 21-30). Most common sample received for processing was Lymph node aspirate accounting to 37% followed by pleural fluid (30%), pus (8%) and gastric lavage amounting for 4% along with other miscellaneous samples making up the others to 21%. Out of 249 MTB detected samples, 47% were from lymph node aspirate, 13% from pleural fluid, 12% from pus, 3% from gastric lavage and 25% from other samples. We noted that the majority of the positive cases were rifampicin sensitive (97.68%).

Conclusion: Results of our study suggest that younger age (third decade of life) and female gender may be independent risk factors for EPTB. In developing countries, the prevalence of EPTB is relatively lower than PTB but still it is an important cause of morbidity and mortality. Thus, early diagnosis and initiation of appropriate treatment are important for reducing the case load. Women especially should be investigated thoroughly for EPTB and BCG vaccination should be encouraged.