CardioExchange Archive

The dramatic growth in type 2 diabetes has resulted in increased interest in screening programs. Now a new study published in the Lancet raises concerns that screening programs may not result in long-term improvement in outcomes.

In the ADDITION-Cambridge study, investigators in the U.K. randomized general practices to either screening or no screening.  The practices allocated to screening were further divided to either intensive cardiovascular risk reduction or standard care. The study population included more than 20,000 adults 40-69 years of age at high risk for undiagnosed diabetes.

Some 3% of patients in the screening groups received a diagnosis of diabetes. After a median follow-up of 9.6 years, there were no significant differences between the screening and control groups.

Rate per 1000 person-years and hazard ratios for the no-screening and the screening group:

• Mortality: 9.89 versus 10.50, 1.06 (CI 0.90-1.25)
• CV mortality: 3.25 versus 3.30, 1.02 (0.75-1.38)

The authors proposed several explanations for the lack of benefit associated withs screening, including ad-hoc screening outside the practice setting in the unscreened group, patients who did not follow the screening program, and concurrent gains in identifying and managing other cardiovascular risk factors during the study period. In addition, the patient population in the study may have been a relatively healthy population with a lower prevalence of undiagnosed diabetes.

The authors concluded that “if population-based screening for diabetes is to be implemented, it should be undertaken alongside assessment and management of risk factors for diabetes and cardiovascular disease and population level preventive strategies targeting underlying determinants of these diseases.”

In a Lancet press release, senior author Simon Griffin said that “the benefits of screening might be smaller than expected and restricted to individuals with detectable disease.  However, benefits to the population could be increased by including the detection and management of cardiovascular risk factors alongside the assessment of diabetes risk, performing repeated rounds of screening, and improving strategies to maximize the uptake of screening.”

In an accompanying comment, Michael Engelgau and Edward Gregg write that prevention programs should screen not just for diabetes but for high-risk individuals as well, though they note that this strategy “assumes that effective prevention programs are available to high-risk cases.” Further, the value of screening depends “on more than just mortality as an outcome,” and will need to include morbidity, quality of life, and costs.