Fasting blood glucose, post-load blood glucose, HbA1c: which best predicts the recurrence of cardiovascular events in non-diabetic coronary patients?

Diabeto-Cardio

Published on 15 oct 2024Lecture 3 min

Given their frequency and their prognostic impact, disorders of glucose tolerance (type 2 diabetes, glucose intolerance, moderate fasting hyperglycemia) must be systematically sought in the presence of cardiovascular pathology. They can be detected by testing fasting blood glucose (FAG) – the option favored by the ADA – or using orally induced hyperglycemia (OGTT) – the gold standard according to the WHO and the only tool to diagnose glucose intolerance. The HbA1c measurement, much more practical than an OGTT, is also proposed by the WHO and the ADA as a means of screening for diabetes (threshold ≥ 6.5%), the American learned society adding that a rate of HbA1c between 5.7% and 6.4% makes it possible to identify patients at high risk of developing type 2 diabetes in the future. In this study, Giulia Ferrannini et al. sought to compare the predictive value of these different indicators (GAJ, blood glucose 2 hours after oral glucose loading G2h, HbA1c) on the risk of occurrence of a new cardiovascular event based on the analysis of data from large studies European cohorts EUROASPIRE IV (EA-IV, 79 centers in 24 countries) and EUROASPIRE V (EA-V, 131 centers in 27 countries). Eligible patients, aged 18 to 80 years, had to be free of diabetes and have been diagnosed with coronary artery disease in the months preceding their inclusion in the study (6 to 36 months in EA-IV, 6 to 24 months in EA- V). Collection of subsequent cardiovascular events was carried out via a questionnaire at least one year after the initial evaluation including OGTT and HbA1c measurement. Analysis of results was limited to participants for whom all these data were available. Among the 16,259 patients included in EA-IV (2012-2013) and EA-V (2016-2017), both OGTT and HbA1c data were available in 8,364 patients (3,932 in EA -IV and 4,432 in EA-V). The average age of the participants was 63.3 years, 75.9% of them were men and 33.3% were obese. At inclusion, a diagnosis of diabetes could be made in 22.5% of patients based on the OGTT results (GAJ ≥ 126 mg/dL and/or G2h ≥ 200 mg/dL) compared to only 4.2 % of patients using only HbA1c (value ≥ 6.5%). An intermediate glucose tolerance abnormality defined by glucose intolerance or moderate fasting hyperglycemia (GAJ 110-125 mg/dL and/or G2h 140-199 mg/dL) was present in 42.1% of participants in the study according to the results of the OGTT when 40.6% of patients had an HbA1c considered predictive of a subsequent risk of type 2 diabetes (value between 5.7% and 6.4%). Average follow-up lasted 1.6 years. During this period, the authors recorded 850 cardiovascular events in 7,892 patients (10.8%) including MI, stroke, cardiovascular death, percutaneous angioplasty, coronary artery bypass grafting or hospitalization for heart failure. In multivariate analysis, GAJ at inclusion is not predictive of the risk of cardiovascular events unlike G2h (from 110 mg/dL) and HbA1c (from 5.7%). A G2h ≥ 162 mg/dL and an HbA1c ≥ 5.9% are the strongest predictive factors for the occurrence of a cardiovascular event (adjusted relative risk 1.58 [IC95% 1,27-1,95] et 1,48 [IC95% 1,19-1,84]respectively). The predictive value of G2h is not modified by the addition of GAJ or HbA1c in the model, and only G2h remains associated with the risk of subsequent cardiovascular events after adjustment including all three variables simultaneously. In total, G2h appears superior to HbA1c in predicting the risk of occurrence of a new cardiovascular event in patients with coronary artery disease while GAJ is not discriminating. Enough to rehabilitate the restrictive OGTT as a screening tool for patients with glucose intolerance so that they can then benefit from appropriate care? At least in coronary patients undoubtedly if we are to believe the results of this study…