Underutilization of Bacteriological Testing in Extrapulmonary Tuberculosis: A Retrospective Single-center Study from Mardin, Türkiye.

Abstract

Objective: Extrapulmonary tuberculosis (EPTB) poses diagnostic challenges due to the low bacillus burden of the disease and the limited use of bacteriological tests. The aim of this study was to evaluate bacteriological confirmation rates, diagnostic methods, and sampling practices among patients diagnosed with tuberculosis (TB) in a southeastern province of Türkiye.

Material and methods: This retrospective study included a total of 456 TB cases diagnosed between 2014 and 2019. The cases were classified as pulmonary tuberculosis (PTB), EPTB, and cases with both types of involvement. Bacteriological and histopathological confirmation rates were compared between the groups.

Results: 41.0% of all cases were classified as EPTB. The most commonly involved site was lymph node TB (22.4%). Bacteriological confirmation rates were significantly lower in EPTB cases: acid-fast bacilli (AFB) smear positivity was 3.2% and culture positivity was 4.3%, whereas the histopathological confirmation rate was 88.8%. No bacteriological samples were taken from 63.1% of patients in the EPTB group. Among PTB cases, AFB smear positivity (71.4%) and culture positivity (66.5%) were significantly higher (P < 0.001).

Conclusion: The findings suggest that bacteriological tests are both underused and of low diagnostic efficiency in EPTB cases. Most diagnoses are based on histopathology rather than on bacteriological confirmation. Strengthening sampling strategies and promoting the use of rapid molecular testing are critical for enhancing bacteriological validation in EPTB.