Cross-cultural adaptation, reliability, and validity of the Persian version of the Lower Limb Functional Index

Noushin Khalilian-Ekrami; Bahram Amirshakeri; Tabassom Ghanavati; Hamid Reza Mokhtarinia; Charles Philip Gabel

doi:10.1016/j.msksp.2022.102626

Cross-cultural adaptation, reliability, and validity of the Persian version of the Lower Limb Functional Index

Musculoskelet Sci Pract. 2022 Dec:62:102626. doi: 10.1016/j.msksp.2022.102626. Epub 2022 Jul 14.

Authors

Noushin Khalilian-Ekrami¹, Bahram Amirshakeri², Tabassom Ghanavati³, Hamid Reza Mokhtarinia⁴, Charles Philip Gabel⁵

Affiliations

¹ Department of Physiotherapy, Faculty of Rehabilitation Sciences, Tabriz University of Medical Sciences, Tabriz, Iran. Electronic address: Noushin.kh.ekradmi@gmail.com.
² Department of Physiotherapy, Faculty of Rehabilitation Sciences, Tabriz University of Medical Sciences, Tabriz, Iran. Electronic address: amirshakerib@tbzmed.ac.ir.
³ Department of Physiotherapy, Faculty of Rehabilitation Sciences, Tabriz University of Medical Sciences, Tabriz, Iran. Electronic address: ghannavatit@tbzmed.ac.ir.
⁴ Department of Ergonomics, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. Electronic address: Hrmokhtarinia@yahoo.com.
⁵ Access Physiotherapy, Sunshine Coast, QLD, Australia. Electronic address: cp.gabel@bigpond.com.

PMID: 35849957
DOI: 10.1016/j.msksp.2022.102626

Abstract

Background: the Lower Limb Functional Index (LLFI) is a regional patient reported outcome measure (PROM) for evaluation of lower limb musculoskeletal functional status. No Persian-language (LLFI-Pr) version is available.

Objectives: LLFI translation and cross-cultural adaptation to Persian and psychometric property evaluation.

Study design: prospective diagnostic assessment.

Methods: to establish the LLFI-Pr face and content validity, double forward-backward translation protocols were used plus cognitive interviews and the 'content validity index'(CVI). Psychometric properties were determined from a convenience sample (n = 307, age 47.18 ± 11.52 years, female = 58.3%) that concurrently completed the LLFI-Pr and Persian Lower Extremity Functional Scale (LEFS-Pr). Test-retest reliability (ICC_2,1, sub-sample, n = 64) was determined during a non-intervention period of 3-7 days. Internal consistency used Cronbach's Alpha (α), error used MDC_90/95 from the SEM, and construct validity used Pearson's r between the LLFI-Pr and LEFS-Pr. Construct validity used exploratory factor analysis (EFA, suppression = 0.30) with non-Gaussian distribution protocols.

Results: psychometric properties were high for test-retest reliability (ICC_2,1 = 0.90) and internal consistency (α = 0.77), moderate for construct validity (r = 0.63), with no floor or ceiling effects, error found SEM = 1.60, MDC₉₀ = 3.7% and MDC₉₅ = 4.42%. A two-factor (EFA) structure (total-variance = 22.01%), that consequently cannot be summated, was determined where five-items failed consistent factor-loading leaving a 20-item version with a high original-LLFI total-equivalency (r = 0.97). However, the general/region-specific item-ratio reduced from the recognized 60/40 ratio to 50/50.

Conclusion: the 20-item LLFI-Pr is a valid two-factor solution with sound psychometric properties for research and clinical Persian-language populations with lower limb disorders.

Keywords: Factor analysis; Lower limb; Patient reported outcomes; Persian; Psychometric.

MeSH terms

Adult
Cross-Cultural Comparison*
Disability Evaluation*
Female
Humans
Language
Lower Extremity
Middle Aged
Prospective Studies
Reproducibility of Results
Surveys and Questionnaires