Avaliação do rastreamento anual da tuberculose na população privada de liberdade dos municípios de Campo Grande e Dourados, Mato Grosso do Sul

Abstract

Background: Tuberculosis (TB) is a major cause of morbidity and mortality among incarcerated populations globally. We performed mass TB screening in 3 prisons and assessed yield, efficiency, and costs associated with various screening algorithms and we evaluated whether the oral swab could be a substitute or supplement for sputum in the diagnosis of TB. Methods: Between 2017 and 2018, inmates from the 3 prisons in Mato Gross do Sul were screened for TB by symptom assessment, chest radiography, sputum testing by Xpert MTB/RIF fourth-generation assay, and culture. Chest radiographs were scored by an automated interpretation algorithm (Computer-Aided Detection for Tuberculosis [CAD4TB]) that was locally calibrated to establish a positivity threshold. Four diagnostic algorithms were evaluated. We assessed the yield (percentage of total cases found) and efficiency (prevalence among those screened) for each algorithm. We performed unit costing to estimate the costs of each screening or diagnostic test and calculated the cost per case detected for each algorithm. For the oral swab sub-study, we enrolled 128 individuals with pulmonary tuberculosis confirmed by sputum Xpert testing, and 128 controls who tested negative by sputum culture and Xpert. We collected two oral swabs by participant, prior to starting treatment. Results: We screened 5,387 prisoners, of whom 214 (3.9%) were diagnosed with TB. Compared to other screening strategies initiated with chest radiography or symptoms, the trial of all participants with a single Xpert MTB/RIF sputum test detected 74% of all tuberculosis cases at a cost of US$249 per case detected. Performing Xpert MTB/RIF screening tests only on those with symptoms had a similar cost per case diagnosed (US$255) but missed 35% more cases (73 vs 54) as screening all inmates. At the oral swab sub-study, the specificity was 100% (128/128). In participants with high mycobaterial load in the sputum, the combined sensitivity was 90% (N = 9/10). In the participants with medium mycobaterial load in the sputum, the combined sensitivity was 79% (N=23/29). Conclusion: In this prospective study in 3 prisons in a high TB burden country, we found that testing all inmates with sputum Xpert MTB/RIF was a sensitive approach, while remaining cost-efficient. These results support use of Xpert MTB/RIF for mass screening in TB-endemic prisons. Our data suggest that oral swab sampling, assayed by Xpert MTB/RIF, has comparable sensitivity to sputum in participants with high and medium mycobacterial load in the sputum. The collection of the oral swab could be a strategy used in prisoners who were unable to collect sputum or in prisons with a high-burden TB. Further studies are needed to identify alternative screening strategies in this population.