Adherence measurement and patient recruitment methods are poor in intervention trials to improve patient adherence.

Objectives: To develop a scale and survey the measurement of patient adherence and patient recruitment, and to explore how these methods impact the results in randomized controlled trials of interventions to improve patient adherence to medications.

Study Design: Analytic survey of a purposively selected sample of patient adherence intervention trials from a systematic review, assessing the quality of adherence measurement and patient recruitment methods.

Results: We identified 44 different measures of adherence, with qualities ranging from valid and objective to unreliable and subjective. The median overall quality of measures of adherence was 5 (interquartile range [IQR], 3; range, 0-9, 9 is high quality). The quality of the measures was associated with variation in the estimate of adherence (Spearman r = 0.66; 95% confidence interval: 0.39, 0.83). The median overall quality of patient recruitment methods was 2 (IQR, 1; maximum score 6, higher is better). There was no significant correlation between the power of the trial to detect an effect and the quality of the patient recruitment methods.

Conclusion: Measurement and recruitment methods in adherence trials varied considerably, and most methods were of low quality. Adherence research could be advanced by using higher quality measures of adherence and better selection and baseline assessment of study participants.