Validation of the Spanish version of the Short-Form Late-Life Function and Disability Instrument

Abstract

Objectives: To validate the Short-Form Late-Life Function and Disability Instrument (SF-LLFDI), a valid measure of functional limitations and disability in older adults, in Spanish-speaking populations and to analyze its psychometric properties.

Design: Validation study.

Setting: Complejo Hospitalario Universitario de Albacete, Spain.

Participants: Sample population of 876 participants aged 70 and older from Albacete, Spain.

Measurements: Forward and back translation of the SF-LLFDI; concurrent validity was determined according to the Barthel Index and the Lawton Scale for disability and according to grip strength, gait speed, the Timed Up and Go Test, and the Short Physical Performance Battery (SPPB) for function. Construct validity, internal consistency, and floor and ceiling effect were determined. The area under the receiver operating characteristic curve (AUC) was calculated to identify function and disability. Intraclass correlation coefficients (ICCs) were used to analyze reliability in a subsample of 50 participants.

Results: The SF-LLFDI was significantly correlated with the Barthel Index (correlation coefficient (r)=0.827), the Lawton Scale (r=0.693), gait speed (r=0.661), and the SPPB (r=0.650). Internal consistency (Cronbach α=0.974), interobserver reliability (ICC=0.989; 95% confidence interval (CI)=0.984-0.993), and intraobserver reliability (ICC=0.982, 95% CI=0.967-0.990) were all excellent. The SF-LLFDI demonstrated excellent discriminant validity, as evidenced by an AUC for a Barthel Index less than 65 points of 0.991 (95% CI=0.986-0.996), with a better cutoff of less than 65 points (sensitivity, 94%; specificity, 94%), and for a Lawton Scale score of less than 4 of 0.976 (95% CI% 0.967-0.985), with a better cutoff of less than 72 (sensitivity, 91%; specificity, 91%). No participant had a maximum score; 36 (4.1%) obtained the minimum.

Conclusion: The Spanish SF-LLDFI is a valid instrument for detecting disability and functional limitation.