Psychometrics of the Patient-Reported Outcomes Measurement Information System Physical Function instrument administered by computerized adaptive testing and the Disabilities of Arm, Shoulder and Hand in the orthopedic elbow patient population

Abstract

Background: This study evaluated the psychometric properties of the Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function (PF) instrument administered through computerized adaptive testing (CAT) compared with the traditional full-length Disabilities of the Arm, Shoulder and Hand (DASH).

Methods: The PROMIS PF CAT and the DASH were administered to 1759 patients seeking care for elbow conditions. This study used Rasch partial credit modeling to analyze the instruments with item fit, internal reliability, response category thresholds, dimensionality, local independence, gender differential item functioning, and floor and ceiling effects.

Results: The PROMIS PF CAT and DASH had satisfactory item fit for all but 1 item on both measures. Internal reliabilities were high for both measures. Two items on the DASH and 4 items on the PF CAT showed nonordered category thresholds. Unidimensionality was adequate, and local independence was supported for both instruments. Gender bias was found for 4 items on the PF CAT and 12 items on the DASH. Both measures had adequate instrument targeting and satisfactory floor and ceiling effects.

Conclusion: The PROMIS PF CAT and the DASH both showed sufficient unidimensionality, good item fit, and good local independence with the exception of high levels of gender item bias, particularly for the DASH. Further scale evaluation should address item bias and item response categories for these instruments. Overall, the PROMIS PF CAT is an effective outcome instrument to measure function in patients with elbow disorders that requires significantly fewer questions than the DASH.

Keywords: DASH; PROMIS; elbow; orthopedics; physical function; psychometric.