The Inventory of Functional Status-Dialysis: development and testing.

Objective: Development and psychometric testing of the Inventory of Functional Status-Dialysis (IFS-Dialysis), which was designed to measure functional status in persons who are receiving chronic incenter hemodialysis treatment.

Design: Three-phase instrument development design: Phase 1--content validity assessment; Phase 2--examination of internal consistency reliability; Phase 3--examination of construct validity.

Sample/setting: 175 chronic hemodialysis patients recruited from an urban, free-standing, outpatient dialysis center.

Methods: Content validity was determined using Popham's average congruency proceudre. Internal consistency reliability was determined using Cronbach's alpha reliability coefficient. Construct validity was examined by bivariate correlations between the IFS-Dialysis and the Karnofsky Performance Scale (KPS), and the Medical Outcomes Study Short Form-36 Health Survey (SF-36) in a subsample of 60 patients.

Results: Content validity was established at 90%. The alpha reliability coefficient for the IFS-Dialysis was 0.86. Subscale alpha coefficients ranged from 0.71-0.82. Correlation between the IFS-Dialysis and the KPS was 0.55. Correlations between the IFS-Dialysis and SF-36 subscales ranged from 0.14-0.53.

Conclusions: The IFS-Dialysis has acceptable content validity, internal consistency, and initial construct validity. Use of the IFS-Dialysis in clinical practice is appropriate.