Failure to complete treatment for latent tuberculosis infection in Portugal, 2013–2017: geographic-, sociodemographic-, and medical-associated factors

There is conflicting evidence about factors associated with failure to complete treatment (FCT) for latent tuberculosis infection (LTBI). We aim to identify the geographic, sociodemographic, and medical factors associated with FCT in Portugal, highlighting the two main metropolitan areas of Porto and Lisbon. We performed a retrospective cohort study including LTBI patients that started treatment in Portugal between 2013 and 2017. We calculated adjusted odds ratios (aOR) and 95% confidence intervals (95% CI) using multivariable logistic regression to identify geographic, sociodemographic, and medical factors associated with FCT. Data on completion of treatment were available for 15,478 of 17,144 patients (90.3%). Of those, 2132 (13.8%) failed to complete treatment. Factors associated with FCT were being older than 15 years (aOR, 1.65 (95% CI = 1.34–2.05) for those aged 16 to 29), being born abroad (aOR, 2.04 (95% CI = 1.19–3.50) for Asia; aOR, 1.57 (95% CI = 1.24–1.98) for Africa), having a chronic disease (aOR, 1.29 (95% CI = 1.04–1.60)), alcohol abuse (aOR, 2.24 (95% CI = 1.73–2.90)), and being intravenous drug user (aOR, 1.68 (95% CI = 1.05–2.68)). Three-month course treatment with isoniazid plus rifampicin was associated with decreased FCT when compared with 6- or 9-month courses of isoniazid-only (aOR, 0.59 (95% CI = 0.45–0.77)). In Lisbon metropolitan area, being born in Africa, and in Porto metropolitan area, alcohol abusing and being intravenous drug user were distinctive factors associated with FCT. Sociodemographic and medical factors associated with FCT may vary by geographical area and should be taken into account when planning interventions to improve LTBI treatment outcomes. This study reinforces that shorter course treatment for LTBI might reduce FCT.