The ratio of diagnosed to undiagnosed diabetes in patients 40 years and older.

A cross-sectional survey of a one in five random sample of apparently healthy adults aged 40 years and older was done in 17 family practice clinics in Newfoundland, in order to pick up previously undiagnosed diabetics, by fasting blood sugar (FBS) measurements. From a sample of 2,087 people, 1,767 were tested. Forty-eight persons had an elevated FBS on the first test, but only 19 had a sustained high FBS when a second test was done. There were 16 previously-known diabetics for each new diabetic found; in this population it was not worth screening healthy persons for diabetes. Testing should be restricted to high-risk people only. As a result of this study, the diabetes prevalence in the 40+ population rose from 12.4% to 13.1%.