A Lower Extremity Physical Function Computerized Adaptive Testing Instrument for Orthopaedic Patients

Background: The aim of this study was to develop a lower extremity (LE) physical function computerized adaptive testing (CAT) instrument based on Patient Reported Outcomes Measurement Information System (PROMIS) physical function items. Methods: The PROMIS physical function item bank was administered to adult outpatient orthopaedic patients. Three hundred eighty-two patients presenting with LE disorders were analyzed using item response theory modeling. A LE physical function item bank was developed by distilling relevant and psychometrically sound items from the full PROMIS physical function bank. Real data CAT simulations were conducted to examine specifications for a live CAT. Results: The LE physical function item bank was sufficiently unidimensional and free of item bias. It demonstrated high reliability along with content and construct validity. The flexible length LE CAT was highly correlated with the full LE instrument and showed uniformly high precision across the entire measurement continuum. The average CAT length was 6 to 7 items when standard error of measurement was 0.3 or less. Conclusion: This LE physical function CAT is a valid, reliable and feasible physical function assessment tool for orthopaedic patients with LE problems that has the potential to reduce patient burden as well as administrative costs associated with data collection.