Psychometric evaluation of medication adherence rating scale (MARS) among Nigerian patients with schizophrenia

The Medication Adherence Rating Scale (MARS) is a 10-item self-report measure of medication adherence in psychosis which is a vital predictor of illness course and outcome in patient with schizophrenia. The initial and subsequent studies have shown that MARS has good reliability and validity scores after correction for the small sample size in the index study.

This study aimed to determine the psychometric properties of MARS among outpatients with schizophrenia at the outpatient clinic of the Neuropsychiatric Hospital Aro Abeokuta Ogun State Nigeria.

Intra-class correlation coefficient (ICC) was used to determine the internal consistency, item-total correlations, and reliability of the instrument. Factor analysis was done using principal component analysis with varimax rotation.

The intra-class correlation coefficient (ICC) for these 10 items (at time T₁) was 0.6 with a P value of <0.001 while for the test--retest analysis was 0.7 with a P value of 0.04. A principal components factor analysis with varimax rotation produced a four-factor solution and factor 4 was found to be the most internally consistent, with Cronbach's alpha of 0.63.

This study supports the internal consistency, test--retest reliability, and constructs validity of the MARS.