Some thoughts on early detection and intervention in diabetes mellitus.

DESPITE the fact that a casual plasma glucose ~200 mg/dl or a fasting plasma glucose > 140 mg/dl on more than one occasion; or a casual blood sugar < 140 mg/dl or fasting values < 100 mg/dl respectively either establishes or reputedly excludes a diagnosis of diabetes [l]; and that both impaired glucose tolerance (IGT) and diabetes appear to meet as many of the criteria for mass screening as hypertension [2], there has been no return to the enthusiasms of the late sixties and early seventies for campaigns of detection and early intervention in the general population. The reasons are not hard to seek. Historically diabetologists were foremost in protesting the long queues of volunteer participants referred from screening surveys to their outpatient clinics as dipstick positive for sugar in the urine or in the blood, and largely negative at follow-up. Predictive values of 28 and sometimes as low as 14% did much to discredit screening in those early days. Then paradoxically, although it was agreed that coronary heart disease in Western cultures was three times as prevalent in diabetic males and six times as prevalent in diabetic females than in corresponding non-diabetics [3], the view in Great Britain was that about 1 or 2% of the general population was diabetic, treatment did not radically alter the outcome, so why deviate resources to case detection? Subsequent experience seems to have borne out the wisdom of this view. As far as coronary heart disease is concerned, an extensive review of the results of 14 longitudinal studies in nine countries, of the relationship of asymptomatic hyperglycemia to coronary heart disease, did not reveal an association that was consistent, strong and graded [4]. It was concluded that asymptomatic hyperglycemia could not be designated an established risk factor for coronary heart disease and the major adult cardiovascular diseases. Thus there seems to be a consensus that with the exception of pregnancy, evidence is lacking that early detection and intervention are beneficial to the majority of undiagnosed diabetics in preventing either complications or mortality [5]. But old enthusiasms die hard. Perhaps in the light of insufficient evidence, especially in the absence of positive contradictory findings, we should give the old Scottish legal verdict of “not proven”; and our College should move towards renewing interest and endorsing support for further studies of early asymptomatic diabetes and IGT in the general population. The point has been made that both non-insulin dependent diabetes mellitus (NIDDM) and, more recently, most insulin dependent diabetes mellitus (IDDM) patients, pass through a phase of varying but often of substantial duration, in which IGT is present. Even if not all IGT patients proceed to diabetes, this is a familiar epidemiological situation which would seem to have excellent experimental potential for prevention. IDDM may have more appeal for the clinician than the epidemiologist but the presence of islet cell (cytoplastic) antibodies at diagnosis of IDDM [6] has potential for even earlier diagnoses. The presence of IGT in some children for periods extending up to three years,