Review: Type 2 diabetes screening does not reduce mortality but treating dysglycemia delays onset of diabetes

A systematic evidence review by the U.S. Preventive Services Task Force (USPSTF) found no evidence of mortality benefit from screening for diabetes, based on 2 large randomized controlled trials (RCTs) conducted in the United Kingdom (UK). However, a number of other studies included in the analysis showed that treatment of impaired fasting glucose or impaired glucose tolerance was associated with delayed progression to diabetes.

The review was published in the June 2 Annals of Internal Medicine and summarized in the June ACP Diabetes Monthly. The following commentary by Michael Tanner, MD, was published in the ACP Journal Club section of the Sept. 15 Annals of Internal Medicine.

Given the results of the review by Selph and colleagues, should the 8 million Americans with undiagnosed diabetes and 86 million with prediabetes be identified, even though 2 RCTs found no mortality benefit from screening?

In 2008, the USPSTF recommended screening for diabetes in people with hypertension, reasoning that those patients should be diagnosed early and receive aggressive blood pressure treatment to a target of 130/80 mm Hg. Now, the American Diabetes Association (ADA) and the Eighth Joint National Committee have agreed on a single blood pressure target for persons with or without diabetes: 140/90 mm Hg.

The 2 UK RCTs of screening, with median follow-up of only 10 years, may have lacked sufficient power to detect a mortality benefit from early diagnosis of this indolent disease, and clear evidence shows that lifestyle changes and medications can delay progression of prediabetes to diabetes. This supports the 2014 USPSTF draft recommendation, which adopts the ADA's more aggressive approach to diabetes screening and targets millions of other high-risk persons, including overweight adults and all persons ≥ 45 years of age.

Diabetes is a patient-important outcome, and its morbidity matters as much as the associated mortality. Therefore, prediabetes is more than just a risk factor. In my view, when prediabetes is detected, some patients may be more likely to make lifestyle changes to stop disease progression and avoid such consequences as neuropathy and visual impairment, as well as eventual heart failure and stroke. Waiting for patients to develop symptoms can allow vascular damage to occur before treatment is initiated. The decision to perform diabetes screening should be made with patients to help identify those who will benefit most.