Development and evaluation of tuberculosis screening scores in Brazilian prisons

Tuberculosis (TB) is highly endemic in Rio de Janeiro State prisons. In addition to TB screening at entry and passive case detection, active case identification may be warranted.

To develop and evaluate performances of scores aimed at identifying "tuberculosis suspects" in order to target TB screening among inmates.

Systematic chest X-ray screening was carried out in two prisons (n=1910). TB was diagnosed among individuals with X-ray abnormalities by sputum microscopic examination and culture or, if bacteriological results were negative, by response to TB treatment. Using this strategy as a reference, the clinical score proposed in WHO guidelines "TB Control in Prisons" was evaluated. Using the same variables in a logistic regression comparing TB and non-TB cases, another score was developed and evaluated. Finally, a 'new score', based on socio-demographic and clinical variables was developed and evaluated.

When applied to our study population (prevalence of active TB: 4.6%), these scores missed many TB cases (sensitivities: 56%, 72%, 74%, respectively). Among the "TB suspects", the probability of finding TB cases was low (positive predictive value: 10%). The scores had high negative predictive values (>97%); specificities (75%, 60%, 67%) were low. Performances were similarly poor for smear-negative and smear-positive cases.

The scores investigated performed poorly and would be unhelpful to target TB screening. Therefore, systematic X-ray screening may be considered, at least during the initial stages of the reinforced TB programme, in order to reduce the impressive burden of TB.