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Generic Drug Discount Programs, Cash-Only Drug Exposure Misclassification Bias, and the Implications for Claims-Based Adherence Measure Estimates

Thompson, Jeffrey A
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1521191260356822

Abstract Details

2018, PhD, University of Cincinnati, Pharmacy: Pharmaceutical Sciences/Biopharmaceutics.
Background: Generic Drug Discount Programs (GDDPs) offer many of the most commonly used prescription drugs at low out-of-pocket costs. GDDP-filled drugs are paid for in cash and not necessarily reported to potential payers. No claims may be generated for such purchases, presenting a problem for health-outcomes researchers and policy makers who rely on claims databases for quality and safety. Objectives: For antidiabetic, statin, and antihypertensive drugs available through GDDP programs that are used in Pharmacy Quality Alliance (PQA) performance measures, the objectives were to: (1) estimate national shares of GDDP-filled prescriptions and patients with GDDP-filled prescriptions; (2) determine patient characteristics associated with GDDP-use; and (3) determine covariates associated with GDDP-use in patients with Medicare or private-only insurance. The fourth objective of this study was to quantify the impact of drug exposure misclassification bias due to missing cash-only prescriptions on antidiabetic, renin-angiotensin system antagonist (RASA), and statin adherence measure estimates. Methods: The Medical Expenditure Panel Survey 2010-2014 was used for this study. Prescriptions were classified as GDDP-filled if the total price paid was out-of-pocket and: 1) the price paid and quantity dispensed exactly matched that provided from a total of 123 GDDP lists issued by 54 different pharmacy chains between 2009 and 2014; 2) the price paid and quantity dispensed was a multiple of the price and quantity listed on a GDDP; or 3) the price paid matched the GDDP price listed from pharmacies with a program stipulation of `up to 30 days’ or `up to 90 days’ and the quantity dispensed was less than the listed 30-day or 90-day quantity. A modified proportion of days covered (PDC) methodology was used to estimate adherence according to PQA-defined methodology. Participants with a PDC = 80% were considered adherent, and for each drug class the proportion of adherent participants when using all prescription claims to calculate PDC was compared to the proportion of adherent participants when removing cash-only claims prior to PDC calculation. Results: From 2010 to 2014 there were over 3.89 billion prescription claims for GDDP-available antidiabetic, statin, and antihypertensive drugs. Of this, 18.5% (n=719,211,220) of claims were cash-GDDP prescriptions and 19.7% (n=768,427,443) of claims were cash-nonGDDP prescriptions. During this period 35.6% of patients filled a cash-GDDP prescription, and overall 60.7% of patients filled any type cash-only prescription. The proportion of adults considered adherent to antidiabetic, RASA, and statin medications were 69.3%, 64.2%, and 64.9%, respectively. Removal of cash-only prescriptions prior to adherence calculation resulted in 13.2% of antidiabetic, 8.9% of RASA, and 7.6% of statin participants misclassified as nonadherent. Conclusion: Cash-only prescriptions, including cash-GDDP and cash-nonGDDP, represent a significant proportion of beta blocker, calcium channel blocker, RASA, oral antidiabetic, and statin drug claims between 2010 and 2014. These results show that the potential magnitude of drug exposure misclassification bias is much larger than previously estimated, and users of claims data to estimate adherence to antidiabetic, RASA, or statin medications should be aware of the potential for drug exposure misclassification bias due to cash-only prescriptions.
Pamela Heaton, Ph.D. (Committee Chair)
Christina Kelton, Ph.D. (Committee Member)
Alex Lin, Ph.D. (Committee Member)
Heidi Luder, PharmD (Committee Member)
Erin Winstanley, Ph.D. (Committee Member)
144 p.
Pharmaceuticals
Misclassification Bias; Generic Drug Discount Programs; Adherence; Medicare Star Ratings; Medical Expenditure Panel Survey; Missing Claims

Recommended Citations

Citations

  • Thompson, J. A. (2018). Generic Drug Discount Programs, Cash-Only Drug Exposure Misclassification Bias, and the Implications for Claims-Based Adherence Measure Estimates [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1521191260356822

    APA Style (7th edition)

  • Thompson, Jeffrey. Generic Drug Discount Programs, Cash-Only Drug Exposure Misclassification Bias, and the Implications for Claims-Based Adherence Measure Estimates. 2018. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1521191260356822.

    MLA Style (8th edition)

  • Thompson, Jeffrey. "Generic Drug Discount Programs, Cash-Only Drug Exposure Misclassification Bias, and the Implications for Claims-Based Adherence Measure Estimates." Doctoral dissertation, University of Cincinnati, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1521191260356822

    Chicago Manual of Style (17th edition)

ucin1521191260356822
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© 2018, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.