Chemoprophylaxis for latent tuberculosis in Far North Queensland: 2015-2019

Abstract

Background: The detection and treatment of latent tuberculosis (LTB) is crucial in controlling the transmission of pulmonary tuberculosis. The Far North Queensland area presents unique challenges in tuberculosis management due to its large catchment, the higher prevalence of tuberculosis in the Indigenous population, and a high rate of migration from tuberculosis-endemic countries. Methods: We performed a retrospective clinical audit of the epidemiology of, and outcomes from, LTB chemoprophylaxis delivered by the Cairns Regional Tuberculosis Control Unit from 2015 to 2019. Results: A total of 583 cases were identified in the five years studied. 464 patients (80%) received 6 months of isoniazid therapy, 62 (11%) received 3 months of isoniazid/rifampicin, 32 (6%) received 9 months of isoniazid, and 21 (4%) received 4 months of rifampicin. Most patients commencing chemoprophylaxis were contacts of active tuberculosis cases (46%) and refugees (32%). A growing proportion of patients were found to have been referred prior to commencement of a TNF-alpha inhibitor (9% in 2019, from 3% in 2015), reflecting the increasing use of biologic therapy in rheumatological conditions. Indigenous patients comprised 9% of all cases. Compliance with treatment was high, with overall completion of treatment observed in 74%. No significant difference in completion rates were observed across different chemoprophylaxis regimes or treatment indications. A significantly higher incidence of side effects was observed in patients receiving 9 months of isoniazid (p=0.0004) compared to other regimens. Only two cases of reactivation tuberculosis occurred despite completion of chemoprophylaxis. Conclusion: Chemoprophylaxis for latent tuberculosis is an effective intervention in Far North Queensland, with the predominant regime being 6 months of isoniazid therapy. Completion rates are high and have improved over time. A longer duration of isoniazid therapy appears to significantly increase the risk of side effects.