Related Experiment Video
Updated: Aug 15, 2025
Digital Home-Monitoring of Patients after Kidney Transplantation: The MACCS Platform
Published on: April 12, 2021
Exploring the Agreement Between Self-Reported Medication Adherence and Pharmacy Refill-Based Measures in Patients
Karumathil M Murali1,2, Judy Mullan2, Steven Roodenrys3
1Department of Nephrology, Wollongong Hospital, Wollongong, NSW, Australia.
Aim:
To assess the quantitative and categorical agreement between two methods of measuring medication adherence: pharmacy refill-based medication possession rates and self-reported medication adherence scale.
Background:
Categorisation of adherence metrics using empirical cut-off scores can lead to misclassification, which can be overcome by expressing adherence as a continuous variable. Pharmacy refill-based adherence can be reported as actual rates, but the validity of expressing self-reported medication adherence scores as a continuous variable to reflect adherence is unknown and its quantitative agreement with refill-based adherence rates untested.
Methods:
Patients with kidney disease, including dialysis patients, from Illawarra Shoalhaven region of New South Wales, Australia were recruited between January 2015 and June 2016 to this cross-sectional study. Medication adherence was assessed using the self-reported Morisky Medication Adherence Scale (MMAS) and two pharmacy refill-based measures, Medication Possession Ratio (MPR) and Proportion of Days Covered (PDC) for antihypertensives and cardiometabolic drugs. Categorical and quantitative agreement between self-reported adherence and pharmacy refill-based adherence were assessed using tests of trend, analysis of covariance (ANCOVA), Cohen's kappa and Bland-Altman analysis.
Results:
We recruited 113 patients. There was a significant declining trend of MPR (p < 0.001) and PDC (<0.001 for antihypertensives, p = 0.004 for cardiometabolic) scores among categories with worsening MMAS adherence. Adjusted ANCOVA showed significant association between self-report and pharmacy refill-based adherence (p < 0.001). Weighted Cohen's kappa statistics showed fair agreement between the self-report and pharmacy refill-based categories. Bland-Altman's analysis showed less than 5% of cases were outside the limits of agreement (-0.36 to 0.27) and the bias for MMAS was negative (-0.05 to -0.09), indicating MMAS did not overestimate adherence.
Conclusion:
There is modest agreement between pharmacy refill-based measures and self-report MMAS measures when assessed categorically or quantitatively. Assessing adherence as a continuous variable should be considered to overcome the challenges associated with categorization of adherence based on arbitrary thresholds.
Related Concept Videos
01:17Factors Affecting Renal Clearance: Renal Impairment
One condition associated with renal failure is uremia. Uremia is characterized by impaired glomerular filtration and fluid accumulation in the body. This condition hinders the renal clearance of drugs, resulting in drug accumulation and potential...
01:11Renal Failure: Dose Adjustments
Reduced renal clearance and elimination rate are common outcomes of renal impairment. These alterations lead to a prolonged elimination half-life and an altered apparent volume of distribution for drugs. As a result, dosage adjustments are typically necessary to maintain optimal drug levels in the body.
However, dosage adjustments...
01:28Chronic Kidney Disease III: Interprofessional Care
01:16Kidney Transplant III: Nursing Management
01:08Renal Drug Clearance: Comparison Between Renal Excretion Methods
Renal clearance is often associated with the renal glomerular filtration rate (GFR), which represents the rate at which plasma is filtered through the glomeruli in the kidney. When drug reabsorption is minimal and there is no active secretion, renal clearance is closely related to the...
01:06Renal Drug Clearance: Overview
Renal clearance can be calculated using different methods. One approach is to divide the urinary drug excretion rate by the plasma drug concentration. This method directly measures renal clearance, indicating the kidneys' efficiency in...