Assessing individual-level measurement precision of the Short Physical Performance Battery using the test information...

Area of Science:

• Gerontology
• Rehabilitation Medicine
• Psychometrics

Background:

• The Short Physical Performance Battery (SPPB) is widely used to evaluate lower extremity function in older adults.
• While SPPB demonstrates group-level validity, its precision for individual-level assessments requires further investigation.
• Elderly patients in cardiac rehabilitation are a key population for assessing functional status.

Purpose of the Study:

• To analyze the psychometric properties of the SPPB, focusing on its measurement precision at the individual level.
• To apply Rasch methods to assess the SPPB's performance in a cohort of elderly cardiac rehabilitation patients.
• To clarify the reliability and accuracy of SPPB scores for individual clinical decision-making.

Main Methods:

• Prospective collection of SPPB data from 637 patients aged 75 years and older admitted to cardiac rehabilitation.
• Classical Rasch analysis to evaluate unidimensionality, item fit, and local independence.
• Calculation of the test information function to determine measurement precision across the score continuum.

Main Results:

• The SPPB demonstrated unidimensionality (84.8% variance), appropriate rating scale function, and good internal construct validity.
• No significant item local dependence was found.
• Individual-level measurement precision was limited, with standard errors exceeding 0.94 logits and confidence intervals covering approximately one-third of the score range.

Conclusions:

• The SPPB exhibits sound psychometric properties for group-level analysis but shows insufficient precision for reliable individual-level interpretation.
• Limited measurement precision may lead to inaccurate clinical decisions regarding diagnosis or change assessment in individual patients.
• Further high-quality research is essential to enhance the SPPB's individual-level measurement accuracy, distinguishing between group and individual change indicators.