Can patients presenting with acute coronary syndrome be screened for diabetes using glycosylated haemoglobin?

The prevalence of diabetes in Australia is 7.4%.1 However, it is three times higher in patients admitted to hospital with acute coronary syndrome (ACS).2 It often remains undetected, and the prevalence of unrecognised diabetes in ACS populations is estimated to be 4%–22%.3 Diabetes is an independent predictor of increased mortality risk after myocardial infarction,4 so that early detection is of particular importance. In Australia, the incorporation of elevated glycosylated haemoglobin (HbA_1c) levels (≥ 48 mmol/mol) into the diagnostic criteria for diabetes in 2012 has facilitated its diagnosis in hospital admissions for ACS.5 HbA_1c levels are not affected by the acute stress of the ACS event, and their assessment does not require a fasting sample. We assessed the feasibility of routinely collecting HbA_1c data as part of a prospective cohort study of consecutive ACS admissions to Monash Health, Victoria. We enrolled patients from 1 January 2013 to 30 June 2014 who were over 21 years of age and fluent in English. HbA_1c was routinely assayed by high-performance liquid chromatography (Arkray Adams Glycohaemoglobin Analyzer HA-8160). The study participants were relatively young, and most were men (Box). Assessment of the prevalence of diabetes was based on self-reports or an HbA_1c value of at least 48 mmol/mol. The overall prevalence of diabetes in the sample was 31% (128/414 patients), with a trend towards lower prevalence in those presenting with ST elevation myocardial infarction (STEMI). Of the 373 patients for whom HbA_1c measurements were available, 102 (27%) had values of at least 48 mmol/mol at the time of presentation. Of the 128 patients classified as having diabetes, 12 cases (9%) had previously been unrecognised. Of the patients with diabetes for whom the relevant data were available, HbA_1c was > 53 mmol/mol in 73 of 117 cases (62%), low-density-lipoprotein cholesterol ≥ 1.8 mmol/L (calculated using the Friedewald formula) in 48 of 75 cases (64%), high-density cholesterol ≤ 1.0 mmol/L in 64 of 84 cases (76%), and triglyceride levels ≥ 2 mmol/L in 41 of 109 cases (38%). Our data confirm a very high prevalence of diabetes in patients with ACS, most of whom had suboptimal diabetes and lipid management on admission. We confirm that it is practicable to measure HbA_1c in consecutive ACS hospital admissions. HbA_1c assessment will have supplementary value in the optimal management of ACS hospital admissions. Hyperglycaemia associated with the acute stress of the ACS event would, however, require measurement of fasting plasma glucose levels.