Development of a computer-adaptive physical function instrument for Social Security Administration disability...

Area of Science:

• Psychometrics
• Disability Assessment
• Health Measurement

Background:

• The Social Security Administration (SSA) requires robust methods to evaluate physical function for disability claims.
• Existing assessment tools may not adequately capture the nuances of physical function relevant to SSA disability programs.
• Development of a specialized instrument is needed to improve the accuracy and efficiency of disability evaluations.

Purpose of the Study:

• To develop and psychometrically test the SSA-Physical Function (SSA-PF) instrument for assessing physical function in SSA disability programs.
• To create a calibrated item bank using item response theory (IRT) for key physical function domains.
• To develop and evaluate computer-adaptive testing (CAT) versions of the SSA-PF instrument.

Main Methods:

• Cross-sectional data collection from SSA claimants (n=1017) and U.S. general population adults (n=999) via telephone and internet surveys.
• Item response theory (IRT) analyses to develop 5 unidimensional SSA-PF scales (Changing & Maintaining Body Position, Whole Body Mobility, Upper Body Function, Upper Extremity Fine Motor, Wheelchair Mobility) comprising 102 items.
• Computer-adaptive testing (CAT) simulations were used to assess the accuracy, reliability, and precision of the developed instruments.

Main Results:

• IRT analyses successfully yielded 5 distinct SSA-PF scales with 102 items, demonstrating unidimensionality.
• Simulated CAT versions showed high accuracy, with strong correlations to full item bank scores and minimal loss in reliability or precision.
• Claimant scores were generally lower than those of the general population sample, indicating a potential shift in physical function levels.

Conclusions:

• The SSA-PF instrument represents a significant methodological advancement for measuring physical function in adults applying for SSA disability benefits.
• The instrument demonstrates broad content coverage across key physical function domains.
• Initial psychometric evaluations indicate the SSA-PF instrument possesses noteworthy reliability and validity for its intended use.