Disparities in Hemoglobin A1c Testing During the Transition to Adulthood and Association With Diabetes Outcomes in Youth-Onset Type 1 and Type 2 Diabetes: The SEARCH for Diabetes in Youth Study

Abstract

Objective: To identify correlates of hemoglobin A_1c (HbA_1c) testing frequency and associations with HbA_1c levels and microvascular complications in youth-onset diabetes.

Research design and methods: The SEARCH for Diabetes in Youth study collected data from individuals diagnosed with diabetes before age 20 at 8 years (n=1,885 type 1, n=230 type 2) and 13 years (n=649 type 1, n = 84 type 2) diabetes duration. We identified correlates of reporting ≥3 HbA_1c tests/year using logistic regression. We examined associations of HbA_1c testing with HbA_1c levels and microvascular complications (retinopathy, neuropathy, or nephropathy) using sequentially adjusted linear and logistic regression.

Results: For type 1 diabetes, odds of reporting ≥3 HbA_1c tests/year at 8 and 13 years diabetes duration decreased with older age at diagnosis (odds ratio [OR] 0.91 [95% CI 0.88-0.95]), longer duration of diabetes (OR 0.90 [0.82-0.99]), not having a personal doctor (OR 0.44 [0.30-0.65]), and lapses in health insurance (OR 0.51 [0.27-0.96]). HbA_1c testing ≥3 times/year over time was associated with lower HbA_1c levels (OR -0.36% [-0.65 to -0.06]) and lower odds of microvascular complications (OR 0.64 [0.43-0.97]) at 13 years duration, but associations were attenuated after adjustment for HbA_1c testing correlates (OR -0.17 [-0.46 to 0.13] and 0.70 [0.46-1.07], respectively). For type 2 diabetes, not seeing an endocrinologist decreased the odds of reporting ≥3 HbA_1c tests/year over time (OR 0.19 [0.06-0.63]), but HbA_1c testing frequency was not associated with HbA_1c levels or microvascular complications.

Conclusions: We observed disparities in HbA_1c testing frequency predominately by health care-related factors, which were associated with diabetes outcomes in type 1 diabetes.

Figure 1

Sociodemographic and clinical correlates of HbA_1c testing cross sectionally at the first SEARCH follow-up visit for type 1 diabetes (top) and type 2 diabetes (bottom). Data are OR (95% CI) for reporting ≥3 tests/year relative to those reporting <3 tests/year. *Core variables of age at diagnosis, diabetes duration, sex, race/ethnicity, and clinical site were not subject to stepwise selection. Candidate variables included parental education at baseline, household income at baseline, diabetes treatment, diabetes care provider, having a personal doctor, having problems with the cost of care in the prior 12 months, type of health insurance, and having continuous health insurance in the prior year. Nonsignificant core variables and nonselected candidate variables are not shown.

Figure 2

Sociodemographic and clinical correlates of HbA_1c testing longitudinally at the first and second SEARCH follow-up visits for type 1 diabetes (top) and type 2 diabetes (bottom). Data are OR (95% CI) for reporting ≥3 tests/year at both visits relative to those reporting <3 tests/year at either visit. *Core variables of age at diagnosis, diabetes duration, sex, race/ethnicity, and clinical site were not subject to stepwise selection. Candidate variables included parental education at baseline, household income at baseline, diabetes treatment, diabetes care provider, having a personal doctor, having problems with the cost of care in the prior 12 months, type of health insurance, and having continuous health insurance in the prior year. Nonsignificant core variables and nonselected candidate variables are not shown. †All variables were allowed to compete in the type 2 model because of the small sample size; only diabetes provider was retained.