Bridging patient-reported outcomes and performance assessments in older adults: linking the Short Physical Performance Battery to the standardised PROMIS Physical Function scale.

SPPB and PROMIS-PF20a demonstrated a high latent correlation in older adults.

• The latent correlation between SPPB and PROMIS-PF20a was 0.89.
• This high correlation supported the feasibility of linking the two instruments onto a common scale.
• The sample consisted of 556 older adults with a mean age of 74 years from different clinical and community-based settings.

Item response theory (IRT) modelling assumptions were fulfilled for the linking of SPPB to PROMIS Physical Function T-scores.

• Assumptions of IRT modelling, including unidimensionality, were investigated and confirmed.
• A unidimensional IRT-based linking model was estimated.
• Participants completed both a generic 20-item PROMIS Physical Function short form (PROMIS-PF20a) and the SPPB sequentially.

Agreement between observed and linked T-scores was stable across several subsamples after linking.

• Cross-walks were derived to convert SPPB scores into standardised PROMIS PF T-scores.
• Agreement between observed and linked T-scores was evaluated across multiple subsamples to assess robustness.
• The stability of agreement across subsamples supports the generalisability of the linking model.

The study produced a user-friendly score cross-walk table to convert SPPB scores to PROMIS PF T-scores.

• The cross-walk table facilitates application in clinical practice and standardisation in geriatric research.
• The linking enables standardised interpretation, comparison, and aggregation of performance-based and self-reported physical function data.
• This addresses a previously identified gap, as commonly used performance-based tools such as the SPPB had remained uncalibrated to the PROMIS Physical Function scale.

The Standardizing-PF project was designed as a prospective cross-sectional study to map patient-reported and performance-based assessments onto a common scale.

• 556 older adults participated, with a mean age of 74 years.
• Participants were recruited from different clinical and community-based settings.
• Both patient-reported (PROMIS-PF20a) and performance-based (SPPB) instruments were administered to each participant.

The lack of standardisation between patient-reported and performance-based physical function tools has limited interpretability and comparability across studies and clinical settings.

• Several patient-reported instruments have been successfully linked to the PROMIS Physical Function scale, but performance-based tools such as the SPPB had not previously been calibrated to this scale.
• This standardisation gap limits integration of physical function data across instruments, studies, and clinical settings.
• Physical function is described as a key outcome in geriatric research.