Clinimetric and psychometric strategies for development of a health measurement scale

Clinimetrics and psychometrics, two accepted methods for developing multiit em health measurement scales, have fundamentally different aims and methods that have seldom been compared and never prospectively. The purpose of thi s study was to determine whether these two methodologies provided comparabl e scales in the development of an upper extremity disability measure. Psych ometric analysis involved field testing a 70-item questionnaire on 407 pati ents. Equidiscriminatory item total correlation (EITC) was used to select t he top 30 items. Clinimetric testing used the mean importance and severity ratings of the 70 items by 76 patients to select the top 30 items. Clinimet ric and psychometric analyses were performed independently. Cronbach's alph a was 0.97 for the top 30 items selected by EITC and 0.96 for the items sel ected based on patient's ratings. The two scales (after clinician modificat ion to improve face validity) shared 16 items in common (P = 0.10). The int raclass correlation coefficient of the patient scores on the two 30-item sc ales was 0.93 before clinician input and 0.97 after. The mean (and standard deviation) difference between scales was 9.1 (8.8) before and 1.7 (5.2) af ter clinician input. A scale developed with a clinimetric strategy can meas ure a complex (so called heterogeneous) clinical phenomenon (thought to be composed of several patient attributes) but still fulfill psychometric crit eria for "homogeneity." Thus, these strategies for the development of healt h measurement scales, which have been considered potentially opposite or co nflicting, may be complementary. J CLIN EPIDEMIOL 52;2:105-111, 1999. (C) 1 999 Elsevier Science Inc.