Validity and reliability of the Staden Schizophrenia Anxiety Rating Scale

Abstract

In schizophrenia, none of the standard anxiety measures exhibit strong psychometric properties, and all performed poorly against quality assessment criteria. Developed for the schizophrenia population, this study examined the validity and reliability of the Staden Schizophrenia Anxiety Rating Scale (S-SARS) that measures both specified and undifferentiated anxiety. Among 353 schizophrenia patients, strong correlations with anxiety parameters supported the S-SARS’s convergent validity. Criterion-related validity testing yielded accuracy, sensitivity, and specificity rates of around 95%. Its discriminant validity was observed for measures of depression, psychosis, akathisia, fatigue, vigour, procrastination, behavioural inhibition and activation, and personal growth and initiative. Structural validity was found in a single-factor unidimensional model with a 0.953 factor score. Excellent results were found for internal consistency (Cronbach’s alpha = 0.931; Spearman–Brown coefficient = 0.937; Guttman split-half coefficient = 0.928) and inter-rater reliability (Krippendorff’s alpha = 0.852). It incurred no more than a small error of measurement whereby the observed scores were within 1.54 to 3.58 of a true score on a zero to 50 scale. These strong psychometric properties suggest that the S-SARS is a valid and reliable instrument for measuring specified and undifferentiated anxiety in schizophrenia, providing the means for the accurate measurement of anxiolytic treatment effects.