Detecting undiagnosed diabetes using glycated haemoglobin: an automated screening test in hospitalised patients

Objective: To assess the utility of glycated haemoglobin (HbA1c) level as an automated screening test for undiagnosed diabetes among hospitalised patients and to estimate the prevalence of undiagnosed diabetes among hospitalised patients. Design, participants and setting: A 3-month prospective study of all adult patients admitted to a tertiary hospital. An HbA1c test was automatically undertaken on admission for all patients with a random plasma glucose (RPG) level ≥ 5.5 mmol/L. Demographic, admission and biochemical data were obtained from hospital databases. A subset of patients was recruited for an oral glucose tolerance test (OGTT) after discharge. Main outcome measures: Prevalence of undiagnosed diabetes (defined as HbA1c ≥ 6.5% in accordance with International Expert Committee and American Diabetes Association recommendations) and utility of automated HbA1c testing. Results: The prevalence of undiagnosed diabetes was 11% (95% CI, 9.8%–12.4%) (262/2360) during the study period. A further 312 patients with known diabetes were admitted. The prevalence of undiagnosed diabetes was highest in the 65–74-years age group. The HbA1c test cost was $152 per new diagnosis of diabetes. Conservatively assuming an annual incidence of undiagnosed diabetes of 0.8%, the ongoing cost of testing hospitalised patients would be $2100 per new diagnosis of diabetes. RPG testing was not sensitive or specific in diagnosing diabetes. Patients were poorly compliant with the post-discharge OGTT (27% completion rate). Conclusions: HbA1c is a simple, inexpensive screening test that can be automated using existing clinical blood samples. Hospital screening for diabetes needs to be coupled with resources for management in the community.