Interferon-gamma release assay for the diagnosis of latent tuberculosis infection in the prison population with a positive tuberculin test: a descriptive study in a prison (Burgos, Spain)

Abstract Objectives: A high prevalence of prison inmates have a positive tuberculin skin test (TST) and sometimes unnecessary treatment for latent tuberculosis infection (LTBI) is prescribed. The prison tuberculosis prevention and control program has not generalized the use of QuantiFERON (QFT) in prisons. We set out to describe the implementation and usefulness of QFT in a population of inmates with positive TST, and to detect false positives and avoid unnecessary treatments. We also analysed the sociodemographic variables of the inmate population. Material and methods: All the positive TST tests between December 2020 and December 2021 from an average population of 300 inmates in Burgos prison were analysed. The QFT value was measured in all the positive cases. Sociodemographic variables were analysed and finally the number of inmates with positive TST, but with a negative QFT result and therefore not requiring LTBI treatment, was evaluated. Results: A total of 41 inmates were included in the study, with a mean age of 44 years. The proportion between Spanish inmates and foreigners was similar. Of all the positive TST, 48.8% were QFT negative. Discussion: It was observed that QFT is a safe method for the diagnosis of LTBI in prisons and that its use would contribute to a more specific selection of inmates who actually need chemoprophylactic treatment for LTBI.