Changes in Screening Practices for Prediabetes and Diabetes Since the Recommendation for Hemoglobin A_1c Testing

Screening involves the presumptive identification of asymptomatic individuals at increased risk for unrecognized disease. We examined changes in screening practices for prediabetes and diabetes since January 2010, when HbA_1c was first recommended as an option for screening and diagnosis.

We studied members without diabetes of an HMO ≥45 years of age continuously enrolled for ≥3 years and assigned to primary care clinicians affiliated with a large academic health system. We defined screening as the first oral glucose tolerance test, HbA_1c, or glucose test performed between 2010 and 2014.

Of 12,772 eligible patients, 9,941 (78%) were screened at least once over 3 years. HbA_1c was the initial screening test 14% of the time and glucose 86% of the time. Of those screened with HbA_1c, 63% had abnormal results defined as HbA_1c ≥5.7% (≥39 mmol/mol). Of those tested with glucose, 30% had abnormal results defined as glucose ≥100 mg/dL, and 5% had abnormal results defined as glucose ≥126 mg/dL. Patients with abnormal HbA_1c levels and those with glucose levels ≥126 mg/dL were equally likely to be scheduled for follow-up appointments (41% vs. 39%), but those with abnormal HbA_1c levels were more likely to be diagnosed with prediabetes or diabetes (36% vs. 26%).

As we observed in 2004, rates of screening are high. HbA_1c is still used less frequently than glucose for screening but is more likely to result in a clinical diagnosis. Evidence to support guidelines to define the role of random glucose screening, including definition of appropriate cut points and follow-up, is needed.