Obesity Alone May Be the Best Predictor of Undiagnosed Diabetes

Laurie Barclay, MD

September 18, 2009

September 18, 2009 — Obesity alone may be the best predictor of undiagnosed diabetes, according to the results of the Diabscreen Study reported in the September/October issue of the Annals of Family Medicine.

"In screening for type 2 diabetes, guidelines recommend targeting high-risk individuals," write Erwin P. Klein Woolthuis, MD, from Radboud University Nijmegen Medical Centre in The Netherlands, and colleagues. "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."

This study was conducted in The Netherlands at 11 family practices with a total practice population of 49,229 patients. Among patients aged 45 to 75 years, the investigators conducted stepwise opportunistic screening as follows: (1) using the electronic medical record, high-risk individuals with 1 or more risk factors for diabetes and low-risk individuals were identified; (2) a capillary fasting plasma glucose measurement was obtained and repeated on a different day if the value exceeded 110 mg/dL; and (3) a venous sample was obtained if both capillary fasting plasma glucose values exceeded 110 mg/dL and at least 1 sample was 126 mg/dL or higher.

Outcome measures included the yield of screening, defined as the percentage of invited patients with undiagnosed diabetes, the number needed to screen (NNS), and the diagnostic value of various risk factors (odds ratio [OR] and area under the receiver operating characteristic curve [AUC]).

There were 3724 high-risk patients seen during usual care who were invited for a first capillary measurement (response rate, 90%), as well as a random sample of 465 low-risk patients contacted by mail (response rate, 86%). Previously undiagnosed diabetes was ultimately detected in 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; P <.01). Screening resulted in the prevalence of diabetes among patients 45 to 75 years old increasing from 6.1% to 6.8%.

Among diagnostic models using a variety of risk factors, the best predictor of undiagnosed diabetes was a model containing obesity alone (OR, 3.2; 95% CI, 2.0 – 5.2; AUC, 0.63).

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

Limitations of this study include the fact that all risk factors are not contained in the diagnostic codes used, the use of fasting plasma glucose rather than oral glucose tolerance, the inability to collect 3 blood samples from all study participants, and the variability in results from portable glucose meters.

"With an opportunistic targeted screening program like ours, diabetes screening in primary care can be performed systematically and continuously, with probably few drawbacks for both patients and health care workers, and with efficient use of resources," the study authors write. "Further research is needed to estimate its cost-effectiveness and limitations. Also, sensitivity and specificity of our stepwise approach need to be studied."

The Netherlands Organisation for Health Research and Development supported this study. LifeScan supported this study and unconditionally provided the blood glucose meters. The authors have disclosed no relevant financial relationships.

Ann Fam Med. 2009;7:422–430. Abstract

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