Social and biological factors associated with unsuccessful TB treatment outcome in Ireland 2011-2021

BACKGROUND: Tuberculosis (TB) treatment success rates are crucial for TB control programme evaluations. The World Health Organisation sets targets of > 90% but Ireland remains below 70%. We analysed notifications from the Irish National TB Surveillance System from 2011-2021 to explore factors associated with successful treatment outcome in Ireland. METHODS: We selected potential predictor variables based on clinical relevance and literature review. We examined each predictor's unadjusted association with treatment success using univariable logistic regression. We used backwards elimination to remove predictors that failed to remain significant in multivariable logistic regression. Treatment success was defined as treatment completed or cured, while unsuccessful treatment was defined as treatment failed, treatment interrupted, transferred out and died from any cause. We used Stata for analysis. RESULTS: Between 2011-2021, 52% of cases were successfully treated, 10.7% were unsuccessfully treated and treatment outcome was not reported for 37%. Treatment outcome completeness declined significantly between 2019-2021. Univariable analysis showed successfully treated cases had higher odds of being a migrant (OR:1.9; 1.5-2.5), being linked to outbreaks (OR:1.9; 1.2-3.0), being a contact of a case (OR: 1.0-2.5;), having a normal X-ray (OR:1.7;1.1-2.6) and being an outpatient (OR:3.0;2.2-4.2). Significant predictors of unsuccessful treatment in the final model were age >70 years, unemployment, immunesuppression and any anti-TB drug resistance. CONCLUSIONS: Surveillance data shows that Ireland fails to meet the WHO target of > 90% treatment success with high levels of missing data. Data quality improvement initiatives are needed to reverse the decline in completeness associated with the Covid-19 pandemic period so control programmes can robustly evaluate performance. Additional supports should be considered for patients who are older, unemployed, immunesuppressed or with drug resistant TB. KEY MESSAGES: • Additional patient supports should be considered for patients who are unemployed, age 70 years and older, immunesuppressed or with drug resistant forms of TB. • Ireland fails to meet the WHO TB treatment success target with high levels of missing data. Treatment outcome completeness needs to be improved so control programmes can robustly evaluate performance.