Background: Type 2 diabetes mellitus (DM) is the leading cause of kidney failure, nontraumatic lower-limb amputations, and new cases of blindness; a major cause of heart disease and stroke; and the seventh leading cause of death in adults in the United States. Screening could lead to earlier detection and earlier or more intensive treatment of persons with asymptomatic DM, impaired fasting glucose (IFG), or impaired glucose tolerance (IGT), potentially resulting in improved clinical outcomes.
Purpose: To systematically update the 2008 U.S. Preventive Services Task Force (USPSTF) review on screening for type 2 diabetes in adults.
Data Sources: We searched the Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews (through March 2014), and MEDLINE® (2007 to March 2014), and manually reviewed reference lists.
Study Selection: Randomized, controlled trials; controlled observational studies; and good-quality systematic reviews on benefits and harms of screening for DM, IFG, or IGT versus no screening; treatment versus no treatment; more versus less intensive glucose, blood pressure, or lipid control interventions; or aspirin use versus nonuse in persons with DM, IFG, or IGT.
Data Extraction: One investigator abstracted data and a second investigator checked data abstraction for accuracy. Two investigators independently assessed study quality using methods developed by the USPSTF.
Data Synthesis (Results): In one good- and one fair-quality trial, screening for DM was associated with no mortality benefit versus no screening, including one trial of patients at higher risk for diabetes (hazard ratio, 1.06 [95% confidence interval, 0.90 to 1.25]). Evidence on harms of screening was limited but indicated no long-term psychological harms. Consistent evidence from multiple trials found that treatment of IFG/IGT was associated with delayed progression to DM. Most trials of treatment for IFG/IGT found no difference in all-cause or cardiovascular mortality, although one trial found that use of lifestyle modification reduced risk of both outcomes after 23 years followup. For screen-detected diabetes, one large fair-quality trial found no effect of an intensive multifactorial intervention on risk of all-cause or cardiovascular mortality versus standard control. For established diabetes (not specifically screen detected), intensive glucose treatment was associated with reduced risk of myocardial infarction and retinopathy, with no effects on mortality. Intensive blood pressure control was associated with a slightly reduced risk of mortality versus standard therapy, but evidence from two recent major trials was mixed. Two trials found that intensive multifactorial interventions were associated with reduced mortality versus standard interventions. Certain pharmacological therapies for screen-detected or early DM, IFG, or IGT were associated with increased risk of withdrawal because of adverse events, hypoglycemia, or hypotension, with no increase in risk of serious adverse events.
Limitations: We did not include non–English language articles. Few studies of treatment were conducted in screen-detected populations.
Conclusions: Screening for DM did not improve mortality after 10 years followup and more evidence is needed to determine effective treatments for screen-detected DM. However, treatment for IFG/IGT was associated with delayed progression to DM.