Randomized Trials Using Provincial Health Numbers for Group Assignment

Purpose: Using data from Ontario, Canada, this report shows how provincial government-assigned health card numbers can be used for individual-level randomization in large pragmatic trials. We describe how health card numbers are assigned and analyze the distribution of health card digits in a trial setting. We then provide an example of how they can be used for randomization and discuss the methodological and practical considerations of the approach.

Key Findings: In Ontario, Canada, health card numbers are randomly generated and assigned without regard to the applicant's characteristics. The number is a 10-digit string connected with hyphens followed by a version code (ie, 1234-567-890-XX). The number is unique to each individual and assigned for life. Before assignment, some numbers within the 10 digits are altered using proprietary business rules. We demonstrate how to use certain digits for individual-level randomization and provide an example of how we will use the tenth digit for randomization in a large new trial of different dialysate bicarbonate concentrations. While this approach has many practical and methodological advantages, it does not allow for stratification. Before using this approach, teams should consider if it will affect the integrity of the randomization and the trial, which will be influenced by the setting and the type of intervention tested.

Implications: Using provincial government-assigned health card numbers for pragmatic randomized trials appears viable, but the merits must be carefully considered on a trial-by-trial basis. The approach can streamline and reduce the cost of conducting such trials.