Psychometric properties of the OARSI/OMERACT osteoarthritis pain and functional impairment scales: ICOAP, KOOS-PS and HOOS-PS.

OBJECTIVES: To evaluate the psychometric properties of the OARSI-OMERACT questionnaires in comparison to the existing validated scales.
METHODS: Consecutive hip or knee osteoarthritis patients consulting in an orthopedic department were enrolled in the study. Data collected were pain using the Intermittent and Constant Osteoarthritis Pain (ICOAP), a Numeric Rating Scale (NRS), the Western Ontario McMaster Universities' Osteoarthritis Index (WOMAC) pain subscale, the Lequesne pain subscale; functional impairment using the Knee disability and Osteoarthritis Outcome Score-Physical Function Shortform (KOOS-PS), the Hip disability and Osteoarthritis Outcome Score-Physical Function Shortform (HOOS-PS), a NRS, the WOMAC function sub-scale, the Lequesne function subscale. Validity was assessed by calculating the Spearman's correlation coefficient between all the scales. Reliability was assessed in out-patients with stable disease comparing the data collected within 2 weeks using the intra-class correlation coefficient (ICC). Responsiveness was assessed on the data from hospitalised patients prior to and 12 weeks after a total joint replacement (TJR) using the standardised response mean.
RESULTS: Three hundred patients (mean age=68 years, females=62%, hip OA=57%) were included. There was a moderate to good correlation between ICOAP, KOOS-PS, HOOS-PS and the WOMAC, NRS and Lequesne scales. Reliability of the ICOAP hip OA HOOS-PS and KOOS-PS was good (ICC range 0.80-0.81) whereas it was moderate for knee ICOAP (ICC=0.65). Responsiveness of the ICOAP, KOOS-PS and HOOS-PS 12 weeks after TJR was comparable to responsiveness of other scales (SRM range: 0.54-1.82).
CONCLUSIONS: The psychometric properties of the ICOAP, KOOS-PS and HOOS-PS were comparable to those of the WOMAC, Lequesne and NRS.