Objective: Validation of a Danish patient safety incident classification adapted from the World Health Organizaton's International Classification for Patient Safety (ICPS-WHO).
Design: Thirty-three hospital safety management experts classified 58 safety incident cases selected to represent all types and subtypes of the Danish adaptation of the ICPS (ICPS-DK).
Outcome measures: Two measures of inter-rater agreement: kappa and intra-class correlation (ICC).
Results: An average number of incident types used per case per rater was 2.5. The mean ICC was 0.521 (range: 0.199-0.809) and the mean kappa was 0.513 (range: 0.193-0.804). Kappa and ICC showed high correlation (r = 0.99). An inverse correlation was found between the prevalence of type and inter-rater reliability. Results are discussed according to four factors known to determine the inter-rater agreement: skill and motivation of raters; clarity of case descriptions; clarity of the operational definitions of the types and the instructions guiding the coding process; adequacy of the underlying classification scheme.
Conclusions: The incident types of the ICPS-DK are adequate, exhaustive and well suited for classifying and structuring incident reports. With a mean kappa a little above 0.5 the inter-rater agreement of the classification system is considered 'fair' to 'good'. The wide variation in the inter-rater reliability and low reliability and poor discrimination among the highly prevalent incident types suggest that for these types, precisely defined incident sub-types may be preferred. This evaluation of the reliability and usability of WHO's ICPS should be useful for healthcare administrations that consider or are in the process of adapting the ICPS.