Inter-rater and intra-rater reliability of disability ratings based on the modified D Code of the ICIDH

Since application of the International Classification of Impairments, Disabilities, and Handicaps (ICIDH) in its full form proved to be impractical, the use of selected parts, or of instruments based on the ICIDH, has been suggested. We have assessed the inter- and intra-rater reliability of disability ratings using a screening instrument, based on the D Code of the ICIDH. The level of functional abilities of all new patients (n = 39) seen by a resident at our outpatient clinic in an 11-week period was rated on a four-point scale for each of 28 items in five ability categories. Independent ratings were done by a resident and his supervisor (inter-rater reliability). Repeated rating by the resident was used to assess intra-rater reliability. Calculation of the inter- and intra-rater reliability was based both on the method of the relative agreement and on the measure kappa. The results showed relative agreements of greater than or equal to 82%, and kappa values of greater than or equal to 0.71 were found. This study shows that in a teaching hospital very satisfactory inter-rater and intra-rater reliabilities using a short instrument based on the D Code of the ICIDH can be achieved. It can therefore be recommended as a method for global disability rating.