Sample size Based on the power of 80% and significance at 0.025 (to allow for two primary comparisons, i.e. DPP-IV vs GLP-1 users and incretin users vs non-incretin users), 216 patients (72 in each of the three groups) will be required to detect a difference of 10 EPC/μl assuming a SD of 19.2 to the power of 24. This sample size will also allow a difference of 8 pg/ml of SDF-1α to be detected with 75% power assuming a SD of 16 to the power of 24.