Psychometric properties of the dutch version of the core measure of melancholia

Background: The CORE measure was designed to assess psychomotor symptoms and the probability of melancholia in depressed people. We tested the inter-rater reliability and validity of the Dutch version of the CORE.

Methods: Thirty-seven elderly, depressed in-patients were studied. The CORE, Salpêtrière Retardation Rating Scale (SRRS), Quick Inventory of Depressive Symptoms-self-report version (QIDS) and Montgomery Asberg Depression Rating Scale (MADRS) were administered. The inter-rater reliability of the CORE was examined by calculating the intra-class correlation coefficient (ICC) of agreement between five independent raters. Construct validity was assessed by calculating Spearman rho (ρ) correlations between CORE and SRRS, QIDS and MADRS measure scores.

Results: The ICC for total CORE scores was 0.80, while, for the CORE sub-scales the ICCs were 0.74 for non-interactiveness, 0.70 for retardation and 0.79 for agitation, indicating high inter-rater reliability. Associations between the CORE and SRRS measures supported the validity of the CORE as a measure of psychomotor disturbance, while correlations between the CORE agitation sub-scale and agitation items derived from the QIDS and MADRS were low to moderate.

Limitations: Both the sample size and the comparator measures of psychomotor disturbance (especially agitation) may have compromised construct validity analyses.

Conclusions: High inter-rater reliability was demonstrated for the Dutch CORE measure. Its validity as a measure of psychomotor disturbance was supported in analyses involving total CORE scores.