Cross-cultural adaptation and measurement properties of the Spanish Foot Care Confidence Scale (FCCS-e) in adults with diabetes receiving primary care.

Objective

To cross-culturally adapt the Foot Care Confidence Scale (FCCS) into Spanish and evaluate its measurement properties in adults with type 1 or type 2 diabetes receiving primary care in Spain.

Methods

A two-phase methodological study was conducted. Phase 1 included translation and back-translation, content validity assessment by 10 experts, and pretesting in 30 participants. Phase 2 included 1026 participants recruited from 30 primary care centres. Structural validity was examined using semi-confirmatory exploratory item factor analysis and Rasch analysis. Internal consistency and construct validity through hypothesis testing were also evaluated.

Results

Overall content validity was favourable (S-CVI/Ave = 0.908), although item 6 showed suboptimal item-level content validity. Factor analysis supported an essentially unidimensional structure (UniCo = 0.994; ECV = 0.910; MIREAL = 0.222), with high internal consistency (ordinal ω = 0.939; α = 0.899). Rasch analysis showed acceptable item fit and local independence, but disordered response-category thresholds and less precise targeting at higher levels of self-efficacy. Of 108 DIF comparisons, 101 (93.5%) were negligible. All four construct-validity hypotheses yielded results in the expected direction.

Conclusion

The FCCS-e showed favourable evidence supporting content validity, structural validity, internal consistency, and construct validity based on hypothesis testing. Further studies should evaluate test-retest reliability, measurement error, responsiveness, and provide additional evidence of construct validity in independent populations and settings.