Diabetes Screening Criteria May Be Inadequate

Taskforce finds current screening recommendations missed detecting more than 50% of diabetes cases

The US Preventive Services Task Force (USPSTF) screening recommendations missed detecting more than 50% of cases of undiagnosed diabetes, according to a recent large cross-sectional study that appeared in the August issue of the American Journal of Preventive Medicine.

In 2008, the Task Force released revised guidelines recommending screening for type 2 diabetes in asymptomatic adults with sustained blood pressure (BP, either treated or untreated) >135/80 mmHg. At that time, the Task Force found no direct evidence on the effectiveness of screening people without symptoms of diabetes, said Task Force member Jessica Herzstein, MD, MPH, who is also Global Medical Director at Air Products, Allentown, PA. 

The Task Force then looked at indirect evidence of the efficacy of screening in reducing cardiovascular disease and found that “available screening tests accurately identified asymptomatic diabetes and that in adults with high BP [defined as 135/80 mmHg and above] and diabetes, more intensive BP treatment led to a substantial reduction—approximately 50%—in cardiovascular events over 5 years,” Dr. Herzstein said. “This was due in part to evidence showing that persons who have diabetes appear to benefit from treatment for lower levels of high BP than do persons who are solely hypertensive. Still, there was insufficient evidence at that time to determine whether screening other populations, including those with BP lower than 135/80 mmHg, would improve long-term outcomes,” she added.

Findings from a Large Cross-Sectional Study

The findings of the current study are based on cross-sectional data from 7,189 adults who participated in the 2003–2010 National Health and Nutrition Examination Survey. All of the participants answered no when asked if they had ever been told that they had diabetes. Undiagnosed diabetes was defined as a fasting plasma glucose ≥126 mg/dL or hemoglobin A1C (A1C) ≥6.5% with no self-report of a diagnosis of diabetes.

Overall, 4.0% of the adults had undiagnosed diabetes. The USPSTF cut-point for diabetes screening (BP >135/80 mmHg) resulted in detecting only 44.4% of those with undiagnosed diabetes (sensitivity) and 74.8% were correctly determined to not have undiagnosed diabetes (specificity). The sensitivity was lower among younger participants.

In addition, a large proportion of people with undiagnosed diabetes who had blood pressure ≤135/80 mmHg had hyperglycemia (23.4% with A1C ≥7.0%) and lipid levels  that may warrant treatment (61.9% with low-density lipoprotein levels ≥100mg/dL) according to guidelines from the American Diabetes Association (ADA), noted the study’s authors. Furthermore, almost half of all patients with undiagnosed diabetes had three or more risk factors for cardiovascular disease, regardless of blood pressure.

Revised USPSTF Criteria To Be Released

The recommendations are updated every 5 years and the Task Force has already begun the process by posting a draft research plan for public comment in May. “The USPSTF hopes that there is new research on screening for type 2 diabetes in asymptomatic non-pregnant adults, including those with BP of 135/80 mmHg or lower since there was not enough evidence available in 2008 to assess the balance of benefits and harms for this group,” Dr. Herzstein said. “Since the Task Force hasn't begun this process yet, we don’t know if new evidence will support targeted or universal screening for diabetes,” she said.

“We hope these analyses will be helpful to the USPSTF when the next recommendations are developed,” said lead author of the study Sarah Stark Casagrande, PhD, Social & Scientific Systems, Inc, Silver Spring, MD. “In addition, we hope that the medical community will consider other strategies and recommendations that incorporate a number of risk factors for identifying people who should be screened for type 2 diabetes,” she said.

Are Better Screening Standards Available?

“The Standards of Care published by the American Diabetes Association (ADA) provide more comprehensive recommendations for screening,” Dr. Casagrande said. “The ADA recommends that overweight adults with at least one additional diabetes-related risk factor be screened. In addition, all adults age 45 years or older should be screened every 3 years. Given that screening is noninvasive and can be quickly and easily performed, criteria should include the strongest risk factors for developing diabetes, specifically obesity, older age, family history of diabetes, and belonging to certain racial/ethnic populations, to identify as many people with undiagnosed diabetes as possible.”

“In the US, current national estimates indicate that 25.6 million adults have diabetes, and 25% to 33% of these people are undiagnosed, which highlights the importance of advanced screening,” Dr. Casagrande noted. “Diabetes screening provides the opportunity to reduce diabetes-related complications and is essential for prompt diagnosis and initiation of individual treatment with the potential to reduce public health burden,” she said.

Dr. Casagrande added that the National Diabetes Education Program (NDEP) has screening tools available at http://ndep.nih.gov/am-i-at-risk/index.aspx.

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