Psychometric evaluation of the medication adherence report scale in caregivers of low-income, urban, African American children with poorly controlled asthma

Abstract

Objective Accurately assessing asthma medication usage among low-income, urban, African American children is essential to reduce asthma health disparities. The purpose of this study was to examine the factor structure of the five-item Medication Adherence Report Scale (MARS), in a sample of caregivers of low-income, urban, African American youth with poorly controlled asthma. Method Using baseline data from a randomized clinical trial evaluating the efficacy of an environmental control educational intervention, confirmatory factor analysis (CFA) was conducted to ascertain the MARS factor structure. Construct validity was assessed using a regression model inclusive of caregiver-reported medication adherence, Asthma Medication Ratio (AMR), asthma control, and caregiver perception of asthma control as predictors of the MARS. Results Caregivers were female (97%) and 27.4% had an annual income under $10,000. The mean MARS score was 21.88 ± 3.33 out of a possible range of 5-25, representing high adherence. Confirmatory factor analysis indicated that a five-item one-factor model marginally fit the data based on the fit indices: 2 (5) = 31.71, p < 0.001; RMSEA ≤ 0.161; CFI = 0.986; TLI = 0.971; and WRMR = 0.979. The MARS was associated with another caregiver-reported measure of medication adherence but not associated with AMR, asthma control, or caregiver perception of asthma control. Conclusions The MARS demonstrated marginal fit in CFA and may not be clinically indicated in light of the lack of associations with objective measures of asthma medication adherence and asthma control.