Prevalence of unrecognized abnormal glucose tolerance in patients attending a hospital hypertension clinic

Diabetes mellitus (DM) and impaired glucose tolerance (IGT) are not uncommonly associated with hypertension. Fasting blood glucose level is still recognized as an indicator of DM. We studied 99 consecutive patients who were not known to be diabetic patients and with no cardiac history, who were attending our Hypertension Clinic for investigation and management of uncontrolled blood pressure (BP). Oral glucose tolerance test (GTT) was carried out and area under the curve for the GTT (AUC-glucose) was calculated. All patients underwent 24-h ambulatory BP monitoring. The GTT was abnormal in 58 patients (58%), indicating IGT in 18, impaired fasting glucose in 16, and DM in 24. The fasting and 120-min glucose level and AUC-glucose in patients with DM on GTT was higher ( P < .0001) than in those with IGT/IFG and in the latter was higher than those with normal GTT. Multiple regression analysis showed that abnormal GTT was independent of the following: level of clinic or ambulatory BP; presence or absence of nocturnal BP dip; cholesterol, sodium, and potassium levels; smoking history; alcohol intake; prior treatment for hypertension; and ethnicity. These results were also independent of antihypertensive medications taken. No significant difference was found in glucose level during GTT, AUC-glucose, or age among the groups of patients receiving diuretics only, those receiving diuretics and β-blockers, and those not receiving any of these agents. The prevalence of glucose abnormalities in hypertensive patients attending a hospital hypertension clinic is sufficiently high to warrant screening for DM and IGT, and fasting glucose levels are not accurate enough for this purpose. All patients attending such a clinic should undergo a GTT.