Population-based Stepwise Screening for Unrecognised Type 2 Diabetes Is Ineffective in General Practice Despite Reliable Algorithms

Christensen JO, Sandbaek A, Lauritzen T, Borch-Johnsen K. Diabetologia. 2004;47:1566-1573.

Given the increasing prevalence of type 2 diabetes, there is a need for screening tools that are effective and easy to use. Although a number of screening tools have been developed, this is one of the few studies that has examined the effectiveness of a proposed screening program in a large general practice population.

A 4-step algorithm was used for the screening and diagnosis of undetected type 2 diabetes, which consisted of (1) a self-administered questionnaire, (2) 2 screening tests (random blood glucose and A1C), (3) a diagnostic test (fasting blood glucose [FBG]), and (4) a second diagnostic test (oral glucose tolerance test [OGTT]). The algorithm was designed to maximize the number of people identified, while minimizing the number of diagnostic tests carried out. The self-administered questionnaire was mailed to 60,926 individuals 40 to 69 years of age from 88 general practices in Denmark, and was used to collect information on age, family history of diabetes, history of high blood pressure, body mass index, and recreational activities.

Results of the questionnaire showed that 11,263 individuals (18.5%) were at high risk for type 2 diabetes and therefore underwent screening. Of these, 30.1% required an FBG diagnostic test and of those tested, 27.2% required an OGTT, the second diagnostic procedure. Overall, 496 individuals (0.8%) were diagnosed with type 2 diabetes.

Compared with recently published prevalence estimates, the detection rate of undiagnosed diabetes was low. Had all 60,926 individuals completed the questionnaire and undergone the screening and diagnostic procedure, 19% (n=2559) would have been expected to have been identified as having type 2 diabetes rather than 0.8% (n=496) of those identified. Investigators attributed the low detection rate to the low questionnaire response rate and concluded that, although the algorithm used was considered reliable, it was ineffective due to a lack of response to the questionnaire.