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

Objective: To assess the utility of glycated haemoglobin (HbA_1c) 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 HbA_1c test was automatically undertaken on admission for all patients with a random plasma glucose (RPG) level ≥5.5mmol/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 HbA _1c ≥6.5% in accordance with International Expert Committee and American Diabetes Association recommendations) and utility of automated HbA _1c 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 HbA_1c 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: HbA_1c 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.