Screening for Type 2 Diabetes in Adults: An Updated Systematic Review

Background: This review was conducted to determine the clinical benefit and potential harms of screening for type 2 diabetes mellitus (T2DM) in asymptomatic adults. Methods: The search strategy from the 2008 US Preventive Services Task Force's framework on type 2 diabetes screening was updated. MEDLINE ® and the Cochrane Database of Systematic Reviews were searched from 2007 to 2012 for systematic reviews, randomized controlled trials and modeling studies. Study quality was assessed using the GRADE System and a standardized review process. Results: Previous results showing benefit of screening among those with high blood pressure were confirmed. No new or old trials were found regarding the effect of screening for T2DM on mortality, cardiovascular mortality and diabetes related complication outcomes. An observational study demonstrated a modest benefit in mortality in an initial cohort invited for T2DM screening (1990-1992), (HR 0.79; 95% CI 0.63, 1.00), but was not replicated in the second cohort invited for screening (2000-2003). Modeling studies reported that population based screening in high-risk individuals (age and hypertension as risk factors) might increase quality adjusted life years and was cost-effective if screening began at age 45 and every three to five years thereafter. Two new randomized controlled trials noted that screening was associated with higher levels of short-term anxiety and worry, but had limited overall psychological impact. Interpretation: This review found no controlled studies of the effectiveness of screening for T2DM, and one observational study demonstrating a modest benefit on mortality. Evidence for the harms associated with screening showed minimal clinical significance. Differences between current and previous evidence can be attributed to the current methodology that integrates the GRADE approach. Recommendations for screening reflect the best available evidence and include screening individuals at high risk for T2DM every 3-5 years with an A1C test, and individuals at very high risk annually with an A1C test.