Adherence to Laboratory Test Requests by Patients with Diabetes: the Diabetes Study of Northern California (DISTANCE)

Objectives: To estimate rates and predictors of clinical laboratory test completion by patients with diabetes after provider referral.

Study Design: Prospective cohort study.

Methods: Among 186,306 adult members with diabetes in Kaiser Permanente Northern California, we searched the electronic medical records (July 1, 2008, to June 30, 2009) of each patient for the first outpatient order to obtain the following laboratory tests commonly used to measure risk factor control or adverse effects of pharmacotherapy: levels of glycosylated hemoglobin, low density lipoprotein cholesterol, serum creatinine, urinary albumin, or creatine kinase (the latter only among persons using statins). We measured laboratory test attendance as completion of an order (including time to results) within 6 months of the referral date and looked for variations by subgroups.

Results: Laboratory test attendance ranged from 86% for glycosylated hemoglobin level to 73% for serum creatinine level. Time to laboratory test attendance was a median of 7 to 11 days and a mean of 25 to 30 days. Laboratory test attendance was more likely for women and older patients or for orders after a face-to-face provider visit and was less likely for orders by a pharmacist. However, most variations (even by laboratory copayment) were small or not clinically substantive. In subanalyses, we observed no clinically significant variations by race/ethnicity, socioeconomic status, trust in provider, or patient-provider communication and found no association with depressive symptoms, health literacy, or English fluency.

Conclusion: The fact that 1 in 7 patients did not complete laboratory tests within 6 months of the provider referral may help explain why healthcare services seem to fall short of optimal diabetes care.