Date of Award

2001

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Pharmaceutical Sciences

First Advisor

Cynthia Willey

Abstract

Objective: Self-report of medication adherence is commonly used in research studies, but the information is lacking about the sensitivity, specificity, reliability and clinical validity of this method. The purpose of this study was to test the sensitivity, specificity and reliability of several methods for accessing medication compliance using patient self-report of adherence. The Medication Event Monitoring System (MEMS) was used as a standard against which self-report measures were compared. Design: Cross sectional study. Data Collection: A self-reported questionnaire accessed compliance of Anti-retroviral therapy (ART) and Protease inhibitors (PI) used by the patients with IIlV infection during the year 1996-1997. The eligibility criteria included ages between 18-74 years, a current prescription of ART or PL One hundred and forty- five patients completed the questionnaire out of which a subset of 86 patients were randomly selected to receive a 30-day supply of their prescribed anti-retroviral in a vial with MEMS Track cap. After a period of one month the data was retrieved using MEMS-4 communicator. Data on demographics, mood status, medical status and clinical characteristics was also obtained by survey. Methodology: Sensitivity, specificity and reliability were calculated for the following self-report measures: number of doses missed in past one month, number of doses missed in past three months, Medication Adherence Scale (MAS) and temptation to skip medication scale. The patient population was divided into two groups, i.e., the patients on PI and patients on ART. MEMS report was used as a standard for comparison of the self-reported compliance. Two different gold standards were set. >80% compliance MEMS and >90% compliance MEMS to test the compliance at 80% and 90% cutoffs. Results: For patients on Protease inhibitors, the agreement between Self-report and MEMS-report according to kappa statistics was K= 0.14 (for >80% compliance MEMS) and K=0.11 (for >90% compliance MEMS) indicating only slight agreement between the two measures of compliance. Number of doses missed in past one month and number of doses missed in the past three months had the highest sensitivity of 1.00, but the specificity of these measures was very poor. MAS had the highest values of kappa (K=0.26) indicating a fair amount of agreement with MEMS. Temptation to skip medication scale showed a good balance of sensitivity and specificity, indicating good accuracy. For patients on ART the agreement between the Self-report and MEMS-report according to the kappa statistics was K=0.15 (for >80% compliance MEMS) and K=0.20 (for >90% compliance MEMS) indicating only slight agreement between the two measures of compliance. In congruence with the results for PI patients, number of dose missed in past one month and number of doses missed in past three months overestimated adherence. MAS had the highest kappa value of K=0.33 indicating fair agreement with MEMS and temptation to skip medication showed a good balance between sensitivity and specificity, similar to PI patients. Conclusion: Sensitivity and specificity are the measures of accuracy of the data. Number of doses missed in past one month and number of doses missed in the past three months showed highest sensitivity, indicating that this measure correctly classified the complaint patients in the complaint category. At the same time these measures had a very low specificity indicating that the non-compliant patients were also incorrectly classified as compliant, causing overestimation of compliance behavior, leading to erroneous results. MAS and temptation to skip medication measures also overestimated adherence, concluding a very low accuracy of these measures in detecting compliance. Kappa statistics is an index of reliability. All the self-report measures only showed a slight to fair agreement with MEMS reported compliance indicating a very low reliability of these self-report measures in measuring compliance. Additional studies will be required to determine if these findings also apply to other populations.

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