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

<b>Objective</b> <p>To identify correlates of hemoglobin A1c (HbA1c) testing frequency and associations with HbA1c levels and microvascular complications in youth-onset diabetes.</p> <p><b>Research Design and Methods</b> </p> <p>The SEARCH for Diabetes in Youth study collected data from individuals diagnosed with diabetes before age 20 at 8 years diabetes duration (n=1,885 type 1, n=230 type 2) and 13 years duration (n=649 type 1, n=84 type 2). We identified correlates of reporting ≥3 HbA1c tests/year using logistic regression. We examined associations of HbA1c testing with HbA1c levels and microvascular complications (retinopathy, neuropathy, or nephropathy) using sequentially adjusted linear and logistic regression. </p> <p><b>Results</b> </p> <p>For type 1 diabetes, odds of reporting ≥3 HbA1c tests/year at 8 and 13 years diabetes duration decreased with older age at diagnosis (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 (0.44 [0.30-0.65]), and lapses in health insurance (OR 0.51 [0.27-0.96]). HbA1c testing ≥3 times/year over time was associated with lower HbA1c levels (-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 HbA1c testing correlates (-0.17 [-0.46 to 0.13]); OR 0.70 [0.46-1.07], respectively). For type 2 diabetes, not seeing an endocrinologist decreased odds of reporting ≥3 HbA1c tests/year over time (OR 0.19 [0.06-0.63]), but HbA1c testing frequency was not associated with HbA1c levels or microvascular complications.</p> <p><b>Conclusions</b> </p> <p>We observed disparities in HbA1c testing frequency, predominately by healthcare-related factors, which were associated with diabetes outcomes in type 1 diabetes.</p>