Describe the study design you will employ in order to determine if your intervention has had an effect on the outcome variable of interest.
- Pre-post for the pilot study, comparing to a control clinic (year before and year after).
- A cluster randomized trial of the CRANIUM intervention compared to treatment as usual will be conducted in 26 Community Behavioral Health (CBHS) clinics in San Francisco County.
Define the unit-of-analysis for your main outcome evaluation, the minimum meaningful effect size, and the sample size necessary to detect this effect size.
The unit-of-analysis for my main outcome evaluation is the patient-level. The two primary study outcomes are 1) evidence of glucose testing determined by glucose-specific serum test or glycated hemoglobin (A1c) and 2) evidence of treatment with metformin (among those with diabetes or positive tests). For my sample size calculation, I will examine the proportion of patients with diabetes screening.
Sample size calculation: Sample size calculation showed that using an intracluster correlation coefficient of 0.02 and an α level of .05, a sample size of 7,800 (13 clinics, with ~300 patients per clinic) would allow for detection of a mean (SD) difference of diabetes screening of 10% (effect size 0.2) in percentage of clients receiving metabolic screening tests with 80% power. To compensate for participant attrition and other potential threats to effect size, including clinic-to-clinic contamination, the target patient sample size was increased by 25% to 9,750. Statistical power may be greater than 80% because analysis will be based on longitudinal methods using data at baseline, 3, 6, and 12 months.