Treating More with Less: Effectiveness and Event Outcomes of Antituberculosis Fixed-dose Combination Drug versus Separate-drug Formulation (Ethambutol, Isoniazid, Rifampicin and Pyrazinamide) for Pulmonary Tuberculosis Patients in Real-world Clinical Practice

Introduction: Conventionally, a combination of four separate drugs (ethambutol, isoniazid, rifampicin, and pyrazinamide [EHRZ]) is the first-line pharmacotherapy for pulmonary tuberculosis (TB). In recent years, fixed-dose combination (FDC) formulation, where a single tablet contains the active ingredients of four aforementioned drugs, is gaining popularity due to its ease of administration.

Objective: To compare the real-world effectiveness of EHRZ and FDC treatment groups on a cohort registry by investigating the sputum conversion rate and treatment outcomes of both groups.

Methods: A total of 11,489 patients' data were extracted from the Sabah TB registry between January 2012 and June 2016, including EHRZ (n = 4188) and FDC (n = 7301) patients. Then, 1:1 propensity score matching was adopted to reduce the baseline bias. Caliper matching was conducted with maximum tolerance score set at 0.001. Confounders included in the propensity score matching were gender, nationality, diabetes, HIV status, smoking status, and chest X-ray status. Successful matching provided 4188 matched pairs (n = 8376) for final analysis.

Results: In this matched cohort of 4188 pairs, the 2-month sputum conversion rate of FDC group was significantly higher than the EHRZ group (96.3% vs. 94.3%; P < 0.001) whereas 6-month sputum conversion of both groups showed no significant difference. Treatment outcomes such as noncompliance rate, failure rate, and success rate have no significant difference (P > 0.05) in both the treatment groups. There was an incidental finding of reduced death rate among FDC group compared to the EHRZ group (0.2% vs. 0.5%; P = 0.034).

Conclusion: The FDC formulation has better sputum conversion rate at 2 months compared to conventional EHRZ regime as separate-drug formulation. It was also observed that FDC has a slight protective effect against all-cause death among TB patients. This protective effect of FDC, however, still needs to be proven further.