Screening for Type 2 diabetes mellitus: a decision analytic approach

Aims Screening for asymptomatic Type 2 diabetes mellitus has been advocated on the grounds that diabetes is a common condition associated with increased morbidity and mortality, but uncertainty remains about the impact of early treatment. This study aimed to determine whether the potential benefits of screening are likely to outweigh the potential harm and to explore which variables significantly influence the balance of benefit and harm resulting from screening. Methods A decision analysis comparing the relative impact of using a single fasting blood glucose screening test, between the ages of 45 and 60 years, with the impact of not screening. The model weighs the increase in quality adjusted life years (QALYs) from reduction in microvascular and cardiovascular complications against the potential decrease in QALYs associated with earlier diagnosis and treatment in an asymptomatic population. Results The baseline model suggests a saving of 10 QALYs for every 10 000 individuals screened: a gain of four from postponed microvascular complications and 17 from avoided cardiovascular complications, as opposed to a loss of 11 as a result of earlier diagnosis in screening detected cases. The balance of benefit and harm is sensitive to baseline cardiovascular risk, the effectiveness of cardiovascular interventions and the relative disutility assigned to early diagnosis and treatment for an individual without symptoms. Conclusions The immediate disutility of earlier diagnosis and additional treatment may be greater than the potential long-term benefit from postponing microvascular complications. Screening decisions should therefore be based largely on consideration of cardiovascular risk and the availability of evidence based interventions to reduce cardiovascular risk.