Empirical evaluation of an ICF core set for managing musculoskeletal conditions in primary care physical therapy services in Spain: a multicenter study

Background Musculoskeletal conditions are a leading cause of disability, yet functioning is not routinely documented in primary care. A setting-specific International Classification of Functioning, Disability and Health (ICF) Core Set may facilitate biopsychosocial assessment by identifying domains relevant to patients and physical therapists. Objective To empirically evaluate category retention and perceived relevance within a specific ICF Core Set for musculoskeletal conditions in primary care physical therapy and examine correspondence and differences between patient-reported and physical therapist-assessed perspectives. Methods A multicenter, cross-sectional study included 387 patient-physical therapist dyads from the public regional healthcare service of Castilla y León (SACYL), Spain. Both perspectives rated 34 ICF categories using a 100 mm VAS. ICF categories with ≥5% prevalence were retained. Sensitivity analyses examined retention across WHODAS 2.0 and Self-administered Comorbidity Questionnaire (SCQ) levels and their continuous associations with ICF summary ratings. Paired perspectives were compared using Wilcoxon signed-rank tests with Holm-adjusted p -values, effect sizes, ICC(2,1), and individual absolute differences exceeding an interpretive 15 mm benchmark. The study was reported according to STROBE. Results All 34 ICF categories exceeded the retention threshold (23.3–94.3%) and remained retained for all disability and comorbidity subgroups. WHODAS 2.0 showed moderate positive correlations with Body Functions and Activities and Participation ratings (Spearman's ρ = 0.329–0.357), whereas SCQ correlations were weaker ( ρ = 0.178–0.202). Absolute paired-score correspondence ranged from moderate to excellent (ICC = 0.697–0.958). Twenty-seven comparisons were significant before adjustment and 20 after Holm adjustment. Differences were generally small (| r | = 0.012–0.356); the largest mean difference was 7.83 mm for “b710 Mobility of joint functions”. Across categories, 5.7%–29.3% of dyads exceeded 15 mm. Discussion The findings provide empirical support for retaining the 34 categories and indicate generally substantial group-level correspondence alongside potentially informative individual differences. Further research should evaluate measurement properties, feasibility, responsiveness, and implementation in routine primary care.