Glycated hemoglobin (HbA1c) is routinely used to assess glycemic control in diabetes, yet the prognostic implications of missing HbA1c values in clinical records are not well defined. A retrospective cohort study using Spain’s BIFAP primary care electronic medical record database evaluated the association between missing baseline HbA1c values and major cardiovascular events or all-cause mortality. The study was published in the Primary Care Diabetes.

The study included 303,199 adults aged ≥30 years with incident diabetes diagnosed between 2005 and 2019. Mean age was 62.2 years, and 44.7% were women. Follow-up began at diagnosis and continued until occurrence of a composite endpoint (major cardiovascular events and/or all-cause death) or December 31, 2019. Mean follow-up was 5.7 years. Baseline HbA1c categories were <7%, 7%–8%, >8%, or missing; 10.2% had no recorded HbA1c. Compared with HbA1c <7%, cardiovascular risk was 1.18 (95% CI 1.14–1.22) for HbA1c 7%–8%, 1.41 (95% CI 1.36–1.46) for HbA1c >8%, and 2.95 (95% CI 2.89–3.05) when HbA1c was missing.

In this national cohort of newly diagnosed diabetes, missing baseline HbA1c values were associated with a higher risk of major cardiovascular events or all-cause mortality.

These findings represent associations observed in routine clinical practice and do not establish causality. Limitations included retrospective design, potential residual confounding, EHR data quality issues, use of all-cause rather than cardiovascular mortality, and possible diagnostic miscoding.