The LLFDI can be used with permission via a one time purchase of the instrument and manual from the Boston University Roybal Center for the Enhancement of Late-Life Function.
Test-retest reliability of the LLFDI has been evaluated over a 1 to 3 week period in 150 ethnically and racially diverse adults over the age of 60 years.
Recently, a study was performed to determine if the LLFDI could be administered via self-report instead of by interview in patients with cardiovascular disease (CVD).
The concurrent validity of the LLFDI was examined by comparing scores with 2 other established self-report instruments, the Short Form-36 physical functioning subscale (PF-10) and the London Handicap Scale (LHS).
Recently the concurrent validity of the LLFDI in patients with CVD has been reported.
The Function Component of the LLFDI was significantly correlated with 6 Minute Walk Test (r = 0.62), Timed-Up-and-Go (r = -0.58), Walking Speed (r = -0.56), and Timed Sit-to-Stand Test scores (r = -0.56).
The function component of the LLFDI has shown extremely high test-retest reliability (intraclass correlation coefficient [ICC] = 0.91 to 0.98) and the disability component has shown moderate to high test-retest reliability (ICC = 0.68 to 0.82) [13-14].
To assess test-retest reliability, two experienced investigators administered the LLFDI to participants in two data-collection sessions separated by 10-14 days.
We assessed validity of the LLFDI by correlating each LLFDI subscale with the BBS and TUG performance tests.
We assessed known-group validity by evaluating whether LLFDI scale scores distinguished between function and disability levels in the physical functioning levels of older adults who used a cane versus walked independently.
Test-retest reliability compared the results of the first and second LLFDI administrations.