OBJECTIVE: Although diabetes is conveniently assessed by self-report, few 
validation studies have been performed. Therefore, we studied whether 
self-report of prevalent and incident diabetes in Women's Health Initiative 
(WHI) participants was concordant with other diagnostic evidence of diabetes.
STUDY DESIGN AND SETTING: A total of 161 808 postmenopausal women aged 50-79 
were enrolled at 40 clinical centers in the U.S. in 1993-1998 and followed 
prospectively. At baseline, prevalent medication treated diabetes was defined as 
a self-report of physician diagnosis and treatment with insulin or oral 
antidiabetic drugs. During followup, incident treated diabetes was defined as a 
self-report of a new physician diagnosis of diabetes treated with insulin or 
oral drugs. Diabetes self-reports were compared with medication inventories and 
fasting glucose levels at baseline and during follow-up.
RESULTS: At baseline, self-reported treated diabetes was concordant with the 
medication inventory in 79% of clinical trial, and 77% of observational study 
participants. Self-reported incident treated diabetes was concordant with the 
medication inventory in 78% between baseline and Year 1 in the clinical trials, 
in 62% between Year 1 and Year 3 in the clinical trials, and in 72% between 
baseline and Year 3 in the observational study. Over similar periods, 99.9% of 
those who did not report treated diabetes had no oral antidiabetic drugs or 
insulin in the medication inventory. At baseline, about 3% not reporting 
diabetes had fasting glucose >126 mg/dl, and 88% of these subjects subsequently 
reported treated diabetes during 6.9 years of follow-up.
LIMITATIONS: Incident self-reported diabetes treated by lifestyle alone was not 
determined in WHI. Medication inventories may have been incomplete and fasting 
glucose may have been lowered by treatment; therefore, concordance with 
self-reported treatment or fasting glucose > or = 126 may have been 
underestimated.
CONCLUSION: In the WHI, self-reported prevalent and incident diabetes was 
consistent with medication inventories, and a high proportion of those with 
undiagnosed diabetes subsequently reported diabetes treatment. Self-reports of 
;treated diabetes' are sufficiently accurate to allow use in epidemiologic 
studies.