Causal inference methodologies to assess the effect of missed clinic visits on treatment success rate among people with tuberculosis in rural Uganda.

BACKGROUND

Although randomized controlled trials are the gold standard design for cause-effect analysis, high costs and challenges around practicability, feasibility, and ethics may limit their use. In such situations, causal inference methods can improve the rigor of cause-effect analysis using observational data but such methods have infrequently been applied in tuberculosis (TB) research. We conducted a parallel comparison across three causal inference methods in order to assess the causal association between missed clinic visit/s and treatment success among people with drug-susceptible bacteriologically confirmed pulmonary TB.

METHODS

We used causal inference methods to analyze cross-sectional data of adults with drug-susceptible bacteriologically confirmed pulmonary TB at clinics in rural eastern Uganda. We compared effect estimates from three causal inference methods, namely instrumental variable analysis, propensity-score analysis (adjustment, matching, weighting, and stratification), and double-robust estimation for cause-effect analysis. The exposure was missing a TB clinic visit/s and the outcome was treatment success defined as cure or treatment completion, both measured on a binary scale. Covariates were selected based on the literature, and their social and biological relevance to the outcome. We report the odds ratio and 95% confidence interval from each causal analysis.

RESULTS

Of 762 participants (mean age of 39.3 ± 15.8 years) included, 186 (24.4%) had missed a clinic visit/s while 687 (90.2%) were successfully treated for TB. Missed clinic visit/s lowered treatment success across all analyses with instrumental variable analysis (OR 0.41, 95% CI 0.20-0.82), propensity-score analysis (adjustment [OR 0.49, 95% CI 0.30-0.82], matching [OR 0.43, 95% CI 0.21-0.91)], weighting [OR 0.52, 95% CI 0.30-0.91], and stratification [OR 0.34, 95% CI 0.19-0.62]), and double-robust estimation (OR 0.49, 95% CI 0.28-0.85).

CONCLUSIONS

Missed clinic visit/s reduced the likelihood of TB treatment success rate across all causal inference methods, supporting a causal relationship. Studies are needed to examine interventions that enhance retention in TB treatment.