Oral glucose tolerance testing in an outpatient heart failure clinic reveals a high proportion of undiagnosed diabetic patients with an adverse prognosis

Abstract

We evaluated the applicability and prognostic importance of oral glucose tolerance testing (OGTT) among outpatients with systolic heart failure (SHF). Consecutive patients with SHF and left ventricular ejection fraction (LVEF) ≤ 45% referred to a heart failure clinic (n= 413) were included in this study. An OGTT was conducted in patients without a history of diabetes. Information on NYHA class, aetiology of SHF, LVEF, treatment, and biochemical parameters were collected at baseline. The survival status was obtained after a median follow-up time of 591 days. Of the 413 patients, 82 (20%) had known diabetes. Of the remaining 331 patients, 227 (69%) agreed to undergo an OGTT. Among the tested subjects, 136 (60%) were classified as having normal glucose tolerance (NGT), 51 (23%) impaired glucose tolerance (IGT), and 40 (18%) newly diagnosed diabetes. Assuming a similar prevalence of unrecognized diabetes among the patients who refused OGTT, the prevalence of diabetes in the total population was 34%. If only fasting blood glucose had been used, 16 of the 40 newly diagnosed diabetic patients would have been undiagnosed. During follow-up, 24 (29%) patients with known diabetes, 6 (15%) of the newly diagnosed diabetic patients, 9 (18%) of those with IGT, and 13 (9%) patients with NGT died. Patients with diabetes had higher mortality rate compared with non-diabetic patients [multivariate hazard ratio 1.89 (1.02-3.59); P = 0.047]. It is feasible to perform diabetes screening using OGTT in outpatients with SHF. A substantial proportion of patients tested were found to have unrecognized diabetes. The presence of diabetes was associated with a higher mortality rate.