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

AIMS:
We evaluated the applicability and prognostic importance of oral glucose tolerance testing (OGTT) among outpatients with systolic heart failure (SHF).
METHODS AND RESULTS:
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].
CONCLUSION:
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.