Reliability and discriminatory testing of a client-based metrology instrument, feline musculoskeletal pain index (FMPI) for the evaluation of degenerative joint disease-associated pain in cats

The objective of this study was to test the readability, reliability, repeatability and discriminatory ability of an owner-completed instrument to assess feline degenerative joint disease (DJD)-associated pain (feline musculoskeletal pain index, FMPI). Readability was explored using four different formulas (Flesch, Fry, SMOG and FOG) and the final FMPI instrument was produced. To assess the instrument, client-owned cats that were defined as normal (normal group) or as having DJD-associated pain and mobility impairment (pain-DJD group) were recruited. A total of 32 client-owned cats were enrolled in the study (normal, n = 13; pain-DJD, n = 19). Owners completed the FMPI on two occasions, 14 days apart. Internal consistency (reliability) and repeatability (test-retest) were explored using Cronbach's α and weighted κ statistic, respectively. Data from the two groups were compared using analysis of covariance (controlling for age) to evaluate discriminatory ability.The FMPI was constructed with 21 questions covering activity, pain intensity and overall quality of life. It had a 6th grade readability score. Reliability of the FMPI was excellent (Cronbach's α > 0.8 for all groupings of questions in normal and pain-DJD cats) and repeatability was good (weighted κ statistic >0.74) for normal and pain-DJD cats. All components of the FMPI were able to distinguish between normal cats and cats with DJD (P < 0.001 for all components). This initial evaluation of the FMPI suggests that this instrument is worthy of continued investigation.