Psychometric properties of the Late-Life Function and Disability Instrument: a systematic review

Background

The choice of measure for use as a primary outcome in geriatric research is contingent upon the construct of interest and evidence for its psychometric properties. The Late-Life Function and Disability Instrument (LLFDI) has been widely used to assess functional limitations and disability in studies with older adults. The primary aim of this systematic review was to evaluate the current available evidence for the psychometric properties of the LLFDI.

Methods

Published studies of any design reporting results based on administration of the original version of the LLFDI in community-dwelling older adults were identified after searches of 9 electronic databases. Data related to construct validity (convergent/divergent and known-groups validity), test-retest reliability and sensitivity to change were extracted. Effect sizes were calculated for within-group changes and summarized graphically.

Results

Seventy-one studies including 17,301 older adults met inclusion criteria. Data supporting the convergent/divergent and known-groups validity for both the Function and Disability components were extracted from 30 and 18 studies, respectively. High test-retest reliability was found for the Function component, while results for the Disability component were more variable. Sensitivity to change of the LLFDI was confirmed based on findings from 25 studies. The basic lower extremity subscale and overall summary score of the Function component and limitation dimension of the Disability component were associated with the strongest relative effect sizes.

Conclusions

There is extensive evidence to support the construct validity and sensitivity to change of the LLFDI among various clinical populations of community-dwelling older adults. Further work is needed on predictive validity and values for clinically important change. Findings from this review can be used to guide the selection of the most appropriate LLFDI subscale for use an outcome measure in geriatric research and practice.

Self-reported function and disability in late life - cross-cultural adaptation and validation of the Swedish version of the late-life function and disability instrument

Purpose

To translate and perform a cross-cultural adaptation of the Late-Life Function and Disability Instrument (LLFDI) to Swedish, to investigate absolute and relative reliability, concurrent validity, and floor and ceiling effects within a Swedish-speaking sample of community-dwelling older adults with self-reported balance deficits and fear of falling.

Method

Translation, reliability and validation study of the LLFDI. Sixty-two community-dwelling, healthy older adults (54 women and 8 men) aged 68–88 years with balance deficits and fear of falling performed the LLFDI twice with an interval of 2 weeks.

Results

Test–retest agreement, intra-class correlation coefficient was very good, 0.87–0.91 in the LLFDI function component and 0.82–0.91 in the LLFDI disability component. The standard error of measure was small, 5–9%, and the smallest real difference was 14–24%. Internal consistency (Cronbach’s alpha) was high (0.90–0.96). Correlation with the SF-36 PCS and PF-10 was moderate in both LLFDI function, r = 0.39–0.68 and r = 0.35–0.52, and LLFDI disability, r = 0.40–0.63 and 0.34–0.57, respectively. There was no floor or ceiling effects.

Conclusion

The Swedish version of the LLFDI is a highly reliable and valid instrument for assessing function and disability in community-dwelling older women with self-reported balance deficits and fear of falling.

Implications for Rehabilitation

The Swedish LLFDI is a highly reliable and valid instrument for assessing function and disability in older women with self-reported balance deficits and fear of falling.

The instrument may be used both in clinical settings and in research.

The instrument is sensitive to change and a reasonably small improvement is enough to detect changes in a group or a single individual.

Factors affecting home care patients' acceptance of a web-based interactive self-management technology

OBJECTIVE

With the advent of personal health records and other patient-focused health technologies, there is a growing need to better understand factors that contribute to acceptance and use of such innovations. In this study, we employed the Unified Theory of Acceptance and Use of Technology as the basis for determining what predicts patients' acceptance (measured by behavioral intention) and perceived effective use of a web-based, interactive self-management innovation among home care patients.

DESIGN

Cross-sectional secondary analysis of data from a randomized field study evaluating a technology-assisted home care nursing practice with adults with chronic cardiac disease. MEASUREMENT AND ANALYSIS: A questionnaire was designed based on validated measurement scales from prior research and was completed by 101 participants for measuring the acceptance constructs as part of the parent study protocol. Latent variable modeling with item parceling guided assessment of patients' acceptance.

RESULTS

Perceived usefulness accounted for 53.9% of the variability in behavioral intention, the measure of acceptance. Together, perceived usefulness, health care knowledge, and behavioral intention accounted for 68.5% of the variance in perceived effective use. Perceived ease of use and subjective norm indirectly influenced behavioral intention, through perceived usefulness. Perceived ease of use and subjective norm explained 48% of the total variance in perceived usefulness.

CONCLUSION

The study demonstrates that perceived usefulness, perceived ease of use, subjective norm, and healthcare knowledge together predict most of the variance in patients' acceptance and self-reported use of the web-based self-management technology.

Creating a computer adaptive test version of the late-life function and disability instrument

BACKGROUND

This study applied item response theory (IRT) and computer adaptive testing (CAT) methodologies to develop a prototype function and disability assessment instrument for use in aging research. Herein, we report on the development of the CAT version of the Late-Life Function and Disability Instrument (Late-Life FDI) and evaluate its psychometric properties.

METHODS

We used confirmatory factor analysis, IRT methods, validation, and computer simulation analyses of data collected from 671 older adults residing in residential care facilities. We compared accuracy, precision, and sensitivity to change of scores from CAT versions of two Late-Life FDI scales with scores from the fixed-form instrument. Score estimates from the prototype CAT versus the original instrument were compared in a sample of 40 older adults.

RESULTS

Distinct function and disability domains were identified within the Late-Life FDI item bank and used to construct two prototype CAT scales. Using retrospective data, scores from computer simulations of the prototype CAT scales were highly correlated with scores from the original instrument. The results of computer simulation, accuracy, precision, and sensitivity to change of the CATs closely approximated those of the fixed-form scales, especially for the 10- or 15-item CAT versions. In the prospective study, each CAT was administered in <3 minutes and CAT scores were highly correlated with scores generated from the original instrument.

CONCLUSIONS

CAT scores of the Late-Life FDI were highly comparable to those obtained from the full-length instrument with a small loss in accuracy, precision, and sensitivity to change.

Validation of the Late-Life Function and Disability Instrument

OBJECTIVES

To assess the concurrent and predictive validity of the Late-Life Function and Disability Instrument (LLFDI).

DESIGN

Cross-sectional.

SETTING

University-based human physiology laboratory.

PARTICIPANTS

One hundred one men and women aged 80.8 +/- 0.4.

MEASUREMENTS

A short physical performance battery (SPPB) and a self-paced 400-m walk (400-m W) were used as performance tests of lower extremity function. The LLFDI was used to assess self-reported function and physical disability. Partial correlations adjusted for age and body mass index were used to determine the concurrent and predictive validity of the LLFDI. Statistical significance was accepted at P<.004 using a testwise correction.

RESULTS

LLFDI Overall Function scores were moderately associated with the SPPB (r=0.65, P<.001), 400-m W gait speed (r=0.69, P<.001), and measures of lower extremity function. Correlations of the two lower extremity subscores of the LLFDI (correlation coefficient (r)=0.63-0.73, P<.001) were greater than for the LLFDI upper extremity subscores (r=0.19-0.26, P>.004). Performance measures of function predicted disability limitations in the range of r=0.37-0.44 (P<.001) and disability frequency in the range of r=0.16-0.20 (P>.004).

CONCLUSION

These findings support the concurrent and predictive validity of the LLFDI. Results support the use of the LLFDI scales as a substitute for physical performance tests when self-report is a preferred data-collection format.