Yield of opportunistic targeted screening for type 2 diabetes in primary care: the diabscreen study

Abstract

Purpose: In screening for type 2 diabetes, guidelines recommend targeting high-risk individuals. Our objectives were to assess the yield of opportunistic targeted screening for type 2 diabetes in primary care and to assess the diagnostic value of various risk factors.

Methods: In 11 family practices (total practice population = 49,229) in The Netherlands, we conducted a stepwise opportunistic screening program among patients aged 45 to 75 years by (1) identifying high-risk individuals (=1 diabetes risk factor) and low-risk individuals using the electronic medical record, (2) obtaining a capillary fasting plasma glucose measurement, repeated on a separate day if the value was greater than 110 mg/dL, and (3) obtaining a venous sample if both capillary fasting plasma glucose values were greater than 110 mg/dL and at least 1 sample was 126 mg/dL or greater. We calculated the yield (percentage of invited patients with undiagnosed diabetes), number needed to screen (NNS), and diagnostic value of the risk factors (odds ratio and area under the receiver operating characteristic curve).

Results: We invited for a first capillary measurement 3,724 high-risk patients seen during usual care and a random sample of 465 low-risk patients contacted by mail. The response rate was 90% and 86%, respectively. Ultimately, 101 high-risk patients (2.7%; 95% confidence interval [CI], 2.2%-3.3%; NNS = 37) and 2 low-risk patients (0.4%; 95% CI, 0.1%-1.6%; NNS = 233) had undiagnosed diabetes (P <.01). The prevalence of diabetes among patients 45 to 75 years old increased from 6.1% to 6.8% as a result. Among diagnostic models containing various risk factors, a model containing obesity alone was the best predictor of undiagnosed diabetes (odds ratio = 3.2; 95% CI, 2.0-5.2; area under the curve=0.63).

Conclusions: The yield of opportunistic targeted screening was fair; obesity alone was the best predictor of undiagnosed diabetes. Opportunistic screening for type 2 diabetes in primary care could target middle-aged and older adults with obesity.

Figure 1.

Study population and algorithm of the screening procedure. cFPG1=first capillary fasting plasma glucose; cFPG2 = second capillary fasting plasma glucose; vFPG = venous fasting plasma glucose; NFG=normal fasting plasma glucose; IFG = impaired fasting glucose. ^a Conversion factor to SI units: x 0.0555.