Incremental yield of the GeneXpert MTB/RIF Assay for the Diagnosis of Pulmonary Tuberculosis in congregates. Case of Muhanga prison/South Province/Rwanda.

Abstract

Background: Tuberculosis remains a major public health problem worldwide and particularly in prison populations. Most of countries are still using conventional tests for TB diagnosis. The aim of this study was to evaluate the incremental yield of Xpert MTB/RIF assay compared to sputum microscopy for TB diagnosis in congregates case of Muhanga prison, Rwanda. Methods: We conducted an analytical, prospective and longitudinal study of TB case detection among 5868 prisoners and 78 staff members of Muhanga prison from 9th December, 2013 to 16th January, 2014. Sputum samples from TB suspects (abnormal CXR, normal CXR with cough) were analysed by Xpert MTB/RIF and Auramine staining microscopy. Results: Among 706 inmates and 5 staff members who were considered TB suspects, a total of 53 TB cases were detected: 20 cases were found on sputum microscopy and 50 on Xpert MTB/RIF tests. Three sputum samples positive on microscopy were not tested by Xpert MTB/RIF due to poor quality. All sputum samples positive for TB on microscopy controlled by Xpert MTB/RIF were found positive. The incremental yield of Xpert MTB/RIF compared to sputum microscopy was 66%. The prevalence rate of pulmonary TB at Muhanga Prison was 7507/100 000, approximately 65.9 times higher compared to the general population (114/100 000). 14.9% of inmates presented with more than one TB cardinal symptoms. Lung infiltrates were predominantly found on CXR (48.6%). One case (1.9%) of RIF resistance was detected by Xpert MTB/RIF. All TB cases detected were male prisoners who were incarcerated for more than 24 months. 17.7% of these prisoners were underweight. Malnutrition (BMI<18.5kg/m2) was associated with TB disease (p=0.007). Among TB suspects, 7.2% were HIV positive. Even if 94.1% of them have already started ARVs, 20.8% had CD4 count less than 200 cells/μl. Conclusion: The study results showed a high prevalence of TB in Muhanga prison. Xpert/ MTB/RIF clearly provided an important incremental yield.