Wat is een reëel verschil bij herhaalde metingen met de Gedragsobservatieschaal voor de Intramurale Psychogeriatrie (GIP)?

The Behavioural Rating Scale for Geriatric Inpatients (GIP) consists of fourteen, Rasch modelled subscales, each measuring different aspects of behavioural, cognitive and affective disturbances in elderly patients. Four additional measures are derived from the GIP: care dependency, apathy, cognition and affect. The objective of the study was to determine the reproducibility of the 18 measures. A convenience sample of 56 patients in psychogeriatric day care was assessed twice by the same observer (a professional caregiver). The median time interval between rating occasions was 45 days (interquartile range 34–58 days). Reproducibility was determined by calculating intraclass correlation coefficients (ICC_agreement) for test-retest reliability. The minimal detectable difference (MDD) was calculated based on the standard error of measurement (SEM_agreement). Test-retest reliability expressed by the ICCs varied from 0.57 (incoherent behaviour) to 0.93 (anxious behaviour). Standard errors of measurement varied from 0.28 (anxious behaviour) to 1.63 (care dependency). The results show how the GIP can be applied when interpreting individual change in psychogeriatric day care participants.