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. 2015 Oct:57:70-4.
doi: 10.1016/j.jsat.2015.05.002. Epub 2015 May 7.

Concordance of Direct and Indirect Measures of Medication Adherence in A Treatment Trial for Cannabis Dependence

Aimee L McRae-Clark  1 , Nathaniel L Baker  2 , Susan C Sonne  3 , C Lindsay DeVane  3 , Amanda Wagner  3 , Jessica Norton  3
Affiliations

Concordance of Direct and Indirect Measures of Medication Adherence in A Treatment Trial for Cannabis Dependence

Aimee L McRae-Clark et al. J Subst Abuse Treat. 2015 Oct.

Abstract

The current study compared adherence rates as measured by two indirect measurement methods (pill count and daily medication diary) to two direct measurement methods (urine riboflavin and serum 6-OH-buspirone level measurement) among participants (n = 109) in a medication treatment trial for cannabis dependence. Pill count and diary data showed high levels of percent agreement and strong kappa coefficients throughout the study. Riboflavin levels indicated lower level of percent in adherence during the study as compared to both pill count and self-report. In the subset of participants with 6-OH-buspirone levels (n = 58), the kappa coefficient also showed low to moderate agreement between the pill count and medication diaries with 6-OH-buspirone levels. In contrast to pill count and medication diaries, adherence as measured by riboflavin and 6-OH-buspirone significantly decreased over time. The findings from this study support previous work demonstrating that pill count and patient self-report of medication taking likely overestimate rates of medication adherence, and may become less reliable as the duration of a clinical trial increases.

Keywords: Adherence; Biological marker; Drug level monitoring; Medication diary; Self-report.

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Conflict of interest statement

Conflict of Interest

The authors have no conflicts of interest related to this work to report.

Figures

Figure 1
Figure 1
Medication adherence over study treatment visits by adherence measurement method for a) all study participants and b) study participants randomized to the buspirone treatment group. * p<0.05 as compared to pill count determined adherence; Ɨ p<0.05 as compared to medication diary determined adherence
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