Screening asymptomatic people for type 2 diabetes does not improve mortality after 10 years of follow-up, but detection and treatment of impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) could delay progression to diabetes.
Those were among the conclusions from a systematic literature review performed by an independent panel to inform upcoming guidelines from the United States Preventive Services Task Force (USPSTF). The draft guidelines, published in October 2014, advised screening for abnormal glucose in adults aged 45 and older and those who are younger with risk factors.
The literature review, published online April 13, 2015 in the Annals of Internal Medicine, is being issued in advance of the USPSTF final recommendation. The six-member panel was chaired by Shelley Selph, MD, from the Oregon Health & Science University Schools of Medicine and Public Health, Portland.
Once finalized, the guidelines will replace the 2008 USPSTF diabetes screening guidelines, which target individuals with high blood pressure. The new focus, reflected in the draft guidelines and informed by the current evidence review of studies published from 2007 through October 2014, shifts instead to identifying people with IFG and IGT.
"The systematic review found that in people with impaired fasting glucose or impaired glucose tolerance — [both] sometimes called 'prediabetes' — progression to diabetes can often be delayed or prevented with lifestyle modifications…or with medications, although medications may be associated with unwanted side effects," Dr Selph told Medscape Medical News.
Little Mortality Benefit in Detecting Diabetes
The authors were unable to find any mortality benefit of detecting type 2 diabetes per se in the literature.
In two 10-year randomized clinical trials — the Anglo-Danish-Dutch Study of Intensive Treatment in People with Screen Detected Diabetes in Primary Care (ADDITION) and a trial conducted in the UK comparing mortality with screening vs no screening (Diabetologia. 2011;54: 312-319) — there was no significant 10-year mortality benefit of detecting diabetes, with hazard ratios close to 1.0 in both studies.
"The literature did not support a 10-year mortality benefit from screening. Only time will tell if there is a mortality benefit to screening beyond 10 years," Dr Selph told Medscape Medical News.
Similarly, in one randomized clinical trial of people with diabetes detected by screening, there was no 5-year mortality benefit or reduction in stroke or heart attack with an intensive multifactorial intervention for screening-detected diabetes aimed at decreasing glucose, lipid levels, and blood pressure, compared with standard glucose, lipid, and blood-pressure lowering therapy.
"Again, only time will tell if there is a benefit to more intensive therapy vs standard therapy beyond 5 years," Dr Selph commented.
In 13 randomized clinical trials examining interventions for screening-detected diabetes, most found no benefit in all-cause or cardiovascular mortality with glucose-lowering or antihypertensive medications or lifestyle modification.
And in nine systematic reviews plus two randomized clinical trials in people with diabetes not specifically detected by screening, no mortality benefit was found with intensive glucose control, while results for intensive blood-pressure control were inconsistent.
However, one trial with a 23-year follow-up did show benefit of lifestyle modification among people with IGT or IFG in reducing both all-cause and CV mortality.
Harms associated with screening included increased anxiety (from three randomized trials) and increased hypoglycemia associated with intensive interventions for people with type 2 diabetes who were not specifically screen-detected (four systematic reviews and six randomized trials).
Prevention of Progression to Diabetes
In contrast to all the negative findings, six studies of lifestyle intervention and eight of pharmacologic intervention found some evidence of delay or prevention of progression from a prediabetic state of IFG or IGT to frank diabetes. Treatment durations ranged from 6 months to 6 years, and follow-up times extended up to 23 years.
The six lifestyle intervention studies (including four from a previous USPSTF review) all showed significant reduction of progression, with a pooled hazard ratio of 0.55.
Use of thiazolidinediones and α-glucosidase inhibitors also reduced progression to diabetes (risk ratios ranging from 0.42 to 0.65). Valsartan and a combination of low-dose metformin and rosiglitazone also reduced progression to diabetes, but nateglinide (Starlix, Novartis) and/or glimepiride did not.
The USPSTF has not yet announced the date for its final recommendation, a task force spokesperson told Medscape Medical News.
The systematic evidence review was funded by the Agency for Healthcare Research and Quality. Dr Selph has no relevant financial relationships. Disclosures for the coauthors are available here.
Ann Intern Med. Published April 13, 2015. Abstract
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Cite this: USPSTF Evidence Review Supports Prediabetes Screening - Medscape - Apr 13, 2015.