Factors associated with screening failure and study withdrawal in multidrug-resistant TB

SETTING: Multidrug-resistant TB (MDR-TB) clinical trial in Lima, Peru and Cape Town, South Africa.OBJECTIVE: To identify baseline factors associated with screening failure and study withdrawal in an MDR-TB clinical trial.DESIGN: We screened patients for a randomized, blinded, Phase II trial which assessed culture conversion over the first 6 months of treatment with varying doses of levofloxacin plus an optimized background regimen (ClinicalTrials.gov: NCT01918397). We identified factors for screening failure and study withdrawal using Poisson regression to calculate prevalence ratios and Cox proportional hazard regression to calculate hazard ratios. We adjusted for factors with P < 0.2.RESULTS: Of the 255 patients screened, 144 (56.5%) failed screening. The most common reason for screening failure was an unsuitable resistance profile on sputum-based molecular susceptibility testing (n = 105, 72.9%). No significant baseline predictors of screening failure were identified in the multivariable model. Of the 111 who were enrolled, 33 (30%) failed to complete treatment, mostly for non-adherence and consent withdrawal. No baseline factors predicted study withdrawal in the multivariable model.CONCLUSION: No baseline factors were independently associated with either screening failure or study withdrawal in this secondary analysis of a MDR-TB clinical trial.