Factors Associated With Attrition in Randomized Controlled Trials of Vocal Rehabilitation: Systematic Review and Meta-Analysis.

OBJECTIVES/HYPOTHESIS: This study aimed to determine the dropout rates and the reasons for dropout in randomized clinical trials of vocal rehabilitation. STUDY DESIGN: This study used systematic review and meta-analysis (CRD42013003807). METHODS: We included randomized controlled trials for voice disorders. In June 2015, we searched the following databases: MEDLINE, EMBASE, Cochrane, Clinical Trials, and AJSLP. The titles and abstracts or full texts of articles were independently analyzed by two reviewers. Study quality was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) scale. Our initial research base included more than 8491 articles. RESULTS: A total of 51 articles were obtained using our eligibility criteria. The low-quality studies evaluated had higher dropout rates (odds ratio: 3.3, 95% confidence interval: 1.04-12.9). Studies with healthy patients (45%) or vocal training versus no training (25%) also had higher dropout rates. Methodological issues seemed to have a greater influence on the dropout rates of the studies included in the co-occurrence matrix. CONCLUSIONS: Dropout rates of approximately 15% occur in randomized clinical trials of speech therapy when assessed by the Grading of Recommendations Assessment, Development and Evaluation. Studies with lower methodological quality had higher patient loss rates. Methodological and clinical reasons accounted for the highest dropout rates in the studies included in this meta-analysis.