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Validity of diabetes self-reports in the Women’s Health Initiative

Jackson, Jody M. RN, BSN1; DeFor, Terese A. MS1; Crain, A. Lauren PhD1; Kerby, Tessa J. MPH, BA2; Strayer, Lori S. MMatSE, MPH3; Lewis, Cora E. MD, MSPH4; Whitlock, Evelyn P. MD, MPH5; Williams, Selvi B. MD, MPH5; Vitolins, Mara Z. DrPH6; Rodabough, Rebecca J. MS7; Larson, Joseph C. MS7; Habermann, Elizabeth B. PhD8; Margolis, Karen L. MD, MPH1

doi: 10.1097/GME.0000000000000189
Original Articles

Objective This study aims to determine the positive and negative predictive values of self-reported diabetes during the Women’s Health Initiative (WHI) clinical trials.

Methods All WHI trial participants from four field centers who self-reported diabetes at baseline or during follow-up, as well as a random sample of women who did not self-report diabetes, were identified. Women were surveyed regarding diagnosis and treatment. Medical records were obtained and reviewed for documented treatment with antidiabetes medications or for physician diagnosis of diabetes supported by laboratory measurements of glucose.

Results We identified 1,275 eligible participants; 732 consented and provided survey data. Medical records were obtained for 715 women (prevalent diabetes, 207; incident diabetes, 325; no diabetes, 183). Records confirmed 91.8% (95% CI, 87.0-95.0) of self-reported prevalent diabetes cases and 82.2% (95% CI, 77.5-86.1) of incident diabetes cases. Among those who never self-reported diabetes, there was no medical record or laboratory evidence for diabetes in 94.5% (95% CI, 89.9-97.2). Women with higher body mass index were more likely to accurately self-report incident diabetes. In a subgroup of participants enrolled in fee-for-service Medicare, a claims algorithm correctly classified nearly all diabetes cases and noncases.

Conclusions Among WHI clinical trial participants, there are high positive predictive values of self-reported prevalent diabetes (91.8%) and incident diabetes (82.2%) and a high negative predictive value (94.5%) when diabetes is not reported. For participants enrolled in fee-for-service Medicare, a claims algorithm has high positive and negative predictive values.

From the 1HealthPartners Institute for Education and Research, Minneapolis, MN; 2HealthPartners Health Improvement and Care Innovation, Minneapolis, MN; 3Epidemiology, University of Minnesota School of Public Health, Minneapolis, MN; 4Department of Medicine, University of Alabama at Birmingham, Birmingham, AL; 5Kaiser Permanente Center for Health Research Northwest, Portland, OR; 6Wake Forest School of Medicine, Winston-Salem, NC; 7Fred Hutchinson Cancer Research Center, Seattle, WA; and 8Department of Surgery, Masonic Cancer Center, University of Minnesota, Minneapolis, MN.

Received August 28, 2013; revised and accepted November 12, 2013.

Funding/support: The Women’s Health Initiative program was funded by the National Heart, Lung, and Blood Institute, National Institutes of Health, US Department of Health and Human Services, through contracts N01WH22110, 24152, 32100-2, 32105-6, 32108-9, 32111-13, 32115, 32118-32119, 32122, 42107-26, 42129-32, and 44221. This analysis was funded by the National Institute of Diabetes and Digestive and Kidney Diseases (grant R21 DK074646 to K.L.M., principal investigator).

Financial disclosure/conflicts of interest: C.E.L. was the principal investigator of a study at the University of Alabama at Birmingham. The University of Alabama at Birmingham received research funding from Novo Nordisk but did not receive any money directly. All other authors declare no conflicts of interest.

Address correspondence to: Jody M. Jackson, RN, BSN, HealthPartners Institute for Education and Research, PO Box 1524, MS 21111R, Minneapolis, MN 55440-1524. E-mail: jody.m.jackson@healthpartners.com

© 2014 by The North American Menopause Society.