WHAT DIFFERENCE DOES A DIAGNOSIS MAKE? Evidence from Marginal Patients

This paper explores the impact of receiving a diagnosis of type 2 diabetes among patients who are close to the diagnostic threshold using a regression discontinuity design. Using data from a large national insurer, we find that a marginally diagnosed patient with diabetes spends $1,097 more on drugs and diabetes-related care annually after diagnosis. This increase in spending persists over the six-year period we observe the patients, despite many who are not initially diagnosed receiving a later diagnosis during this time frame. These marginally diagnosed patients experience improved blood sugar after the first year of diagnosis. However, this improvement is not statistically significant in subsequent years, and in some post-test years our confidence intervals rule out any improvement in this measure. Other clinical measures of health (cholesterol and mortality) do not change significantly at the cutoff, although our confidence intervals include meaningfully sized effects. The diagnosis rates for preventable disease-related conditions such as diabetic retinopathy, neuropathy, and kidney disease increase following a diagnosis, likely because of more intensive screening.