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
Authors: Sauder Katherine A. , Stafford Jeanette M. , Ehrlich Shelley , Lawrence Jean M. , Liese Angela D. , Marcovina Santica , Mottl Amy K. , Pihoker Catherine , Saydah Sharon , Shah Amy S. , D’Agostino Ralph B. , Dabelea Dana ,   SEARCH for Diabetes in Youth Study Group, Lawrence Jean M. , Hung Peggy , Koebnick Corinna , Li Xia , Lustigova Eva , Reynolds Kristi , Pettitt David J. , Mayer-Davis Elizabeth J. , Mottl Amy , Thomas Joan , Jackson Malaka , Knight Lisa , Liese Angela D. , Turley Christine , Bowlby Deborah , Amrhein James , Apperson Elaine , Nelson Bryce , Dabelea Dana , Bellatorre Anna , Crume Tessa , Hamman Richard F. , Sauder Katherine A. , Shapiro Allison , Testaverde Lisa , Klingensmith Georgeanna J. , Maahs David , Rewers Marian J. , Wadwa Paul , Daniels Stephen , Kahn Michael G. , Wilkening Greta , Bloch Clifford A. , Powell Jeffrey , Love-Osborne Kathy , Hu Diana C. , Dolan Lawrence M. , Shah Amy S. , Standiford Debra A. , Urbina Elaine M. , Pihoker Catherine , Hirsch Irl , Kim Grace , Malik Faisal , Merjaneh Lina , Roberts Alissa , Taplin Craig , Yi-Frazier Joyce , Beauregard Natalie , Franklin Cordelia , Gangan Carlo , Kearns Sue , Klingsheim Mary , Loots Beth , Pascual Michael , Greenbaum Carla , Imperatore Giuseppina , Saydah Sharon H. , Linder Barbara , Marcovina Santica M. , Chait Alan , Clouet-Foraison Noemie , Harting Jessica , Strylewicz Greg , D’Agostino Ralph , Jensen Elizabeth T. , Wagenknecht Lynne E. , Casanova Ramon , Divers Jasmin , Goldstein Maureen T. , Henkin Leora , Isom Scott , Lenoir Kristin , Pierce June , Reboussin Beth , Rigdon Joseph , South Andrew Michael , Stafford Jeanette , Suerken Cynthia , Wells Brian , Williams Carrie 
Published: August 2021

OBJECTIVE
To identify correlates of hemoglobin A1c (HbA1c) testing frequency and associations with HbA1c 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 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.

RESULTS
For type 1 diabetes, odds of reporting ≥3 HbA1c 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]). HbA1c testing ≥3 times/year over time was associated with lower HbA1c 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 HbA1c 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 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.

CONCLUSIONS
We observed disparities in HbA1c testing frequency predominately by health care–related factors, which were associated with diabetes outcomes in type 1 diabetes.