Population-based stepwise screening for unrecognised Type�2 diabetes is ineffective in general practice despite reliable algorithms

Abstract

Aims/hypothesis. The yield of screening programmes for Type 2 diabetes in the existing healthcare setting might be lower than anticipated from tests of screening algorithms in data from epidemiological surveys. Our aims were to evaluate the reliability of the algorithms and the effectiveness of a proposed stepwise screening programme for Type 2 diabetes in general practice. Methods. The screening programme had four steps: (i) mail-distributed self-administered risk-chart; (ii) screening tests: random blood glucose (RBG) and HbA 1 c; (iii) diagnostic procedure 1 for fasting blood glucose (FBG) (if RBG ≥5.5 mmol/l or HbA 1 c ≥6.1%); and (iv) OGTT as diagnostic procedure 2 (if 5.6≤FBG<6.1 mmol/l or HbA 1 c ≥6.1%). Abnormalities of glucose metabolism were classified according to the WHO 1999 criteria, based on capillary whole blood. The subjects were all patients between 40 and 69 years of age (n=60,926) who were registered in 88 general practices and had not been previously diagnosed with diabetes.Results. A total of 11,263 individuals had a high-risk risk-score and attended the screening consultation (step 1 test-positive). Of these, 30.1% needed diagnostic tests (step 2 test-positive) and 27.2% of these needed an OGTT (step 3 test-positive). The test-positive proportions were equal to the proportions obtained in data from a population-based survey from Step 2 onwards, and the algorithms were thus reliable. The identification rate was only 19% of all prevalent undiagnosed diabetes according to a recently published prevalence estimate. This was due to a large dropout rate among high-risk individuals prior to entry into the programme. Conclusions/interpretation. Population-based maildistributed stepwise screening for Type 2 diabetes in general practice is ineffective, despite reliable screening algorithms, primarily because many high-risk individuals fail to participate.

Progression from impaired fasting glucose and impaired glucose tolerance to diabetes in a high-risk screening programme in general practice: the ADDITION Study, Denmark

“…All persons aged 40-69 years, registered with the participating practices, received an invitation letter with a risk score. The risk score for diabetes was developed in a general population-based screening study in Denmark (the Inter99 study) and validated in the pilot study for the ADDITION study [7,8]. Patients with a risk score of 5 points or more ( Fig.…”

“…Individuals were considered at low risk of having diabetes if RBG was <5.5 mmol/l and HbA 1c <5.8%. Cut-points for RBG and HbA 1c were also based on the pilot study with a sensitivity of 85.7%, a specificity of 75.7% and a testpositive fraction of 27.7% when used combined [7]. In all those who proceeded in the programme after this second step, fasting blood glucose (FBG) was measured.…”

“…All practices were supervised by the HemoCue Company in analysing the blood samples and the daily calibration of the machines [7]. FBG was taken after an overnight fast, where the persons were instructed not to eat, drink or smoke later than 23 h the evening before.…”

Determinants of progression from impaired fasting glucose and impaired glucose tolerance to diabetes in a high-risk screened population: 3 year follow-up in the ADDITION study, Denmark

“…The screening programme in Denmark and the 1 year follow-up of IFG and IGT have been evaluated previously [1,18]. The The screening process The screening process was a stepwise, decision-tree model.…”

“…The The screening process The screening process was a stepwise, decision-tree model. Persons aged 40 to 69 years, registered with the participating practices in five counties in Denmark, received an invitation with a risk score questionnaire [18,19]. Persons with a risk score of 5 points or more were recommended to contact their general practitioners for further tests.…”