Background: Pulmonary tuberculosis (PTB) is a communicable disease and one of the major health problems worldwide. PTB is also a major health problem in prisons. Previously chest radiography and conventional acid fast bacilli smear were used in screening PTB but with low sensitivity and specificity. Sputum culture is a gold standard for PTB diagnosis but time-consuming. Xpert MTB/RIF provided high sensitivity and specificity for detection of tuberculosis and rifampin resistance directly from sputum in less than two hours. In Thailand Xpert MTB/RIF was mostly used in high risk multi-drug resistant suspected cases. Xpert MTB/RIF was combined with mass-screening chest radiography in prisoners for PTB and early detection of multidrug resistant TB. However, factors affecting Xpert MTB/RIF results in prisoner are not well understood, and the present study was undertaken to examine the factors affecting of Xpert MTB/RIF results in prisoners.

Objective: To estimate the prevalence of PTB in four prisons in Songkhla Province, and assess the factors affecting the results of Xpert MTB/RIF assay.

Materials and Methods: A cross-sectional survey in prisoners from four prisons in Songkhla Hospital was conducted between April 2018 and September 2018.

Results: The calculated prevalence of probable PTB cases was 2,832 per 100,000 prisoners. From 10,626 prisoners, 301 cases of PTB were detected from the mass-screening. Factors associated with a positive Xpert MTB/RIF result were type of prison (adjusted OR 0.38; 95% CI 0.22 to 0.65), previous TB infection (adjusted OR 0.36; 95% CI 0.21 to 0.60), having at least one TB symptom (adjusted OR 1.9; 95% CI 1.18 to 3.05), and having reticulopatchy infiltration lesion (adjusted OR 3.35; 95% CI 1.88 to 5.97).

Conclusion: The four prisons had a high prevalence of PTB. Xpert MTB/RIF is a useful diagnostic tool for early detection of PTB in prisoners. However, patients’ factors affecting Xpert MTB/RIF results should be considered before the assay is performed.

Keywords: Pulmonary tuberculosis, Prisoners, Xpert MTB/RIF assay, Chest radiography

Received 11 Dec 2019 | Revised 23 Mar 2020 | Accepted 24 Mar 2020