Glucose Intolerance and Hypertension in North London: The Islington Diabetes Survey

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Abstract
In a general practice‐based screening survey, 1040 (63.3%) of a randomly selected sample of 1644 people over the age of 40 years were examined for diabetes mellitus (DM) and hypertension (HT). Glucose intolerance was assessed by a single 2 h post‐load blood glucose estimation and HT (diastolic blood pressure ≥95mmHg by a single blood pressure reading) or being on anti‐hypertensive treatment.The sample included 41 patients (2.1%) with known DM and 135 (12.5%) with known HT. Screening identified 27 (2.6%) new diabetics (16 women) and 43 subjects (4.1%) with impaired glucose tolerance (30 women). A further 30 known diabetics over the age of 40 and 12 diabetics under 40 were registered at the practice. The estimated prevalence of diabetes in the over 40s was 4.6% and in all ages was 1.6%. DM appeared to affect Afro‐Caribbeans more commonly than Caucasians among those examined (5.9% versus 2.6%) though this difference did not reach statistical significance (z = 1.1106, p=0.134).A total of 190 subjects (17.5%) were found to have HT, of whom 55 (5.1%) were newly diagnosed; 10.2% of the sample were on anti‐hypertensive treatment, and in 79.3% of these the blood pressure was well controlled (diastolic z=4.206, p<0.001).This survey shows that the prevalence of DM diagnosed according to modern diagnostic criteria appears to be similar to that found in previous surveys using older criteria. The sensitivity and specificity of the 2hBG as a screening test for DM (with 95% confidence limits) were 69.2±25.1% and 97.4±2.3%, respectively. In 49 subjects glucose tolerance status changed on formal glucose tolerance testing. The use of a single 2hBG in screening for DM gave a false negative rate of 40%. It is concluded that a single 2hBG is not sufficiently sensitive as a screening test for DM in population screening. The prevalence of HT is higher than has been noted in previous general practice surveys.