Evaluation of a preliminary physical function item bank supported the expected advantages of the Patient-Reported Outcomes Measurement Information System (PROMIS).
OBJECTIVE
The Patient-Reported Outcomes Measurement Information System (PROMIS) was initiated to improve precision, reduce respondent burden, and enhance the comparability of health outcomes measures. We used item response theory (IRT) to construct and evaluate a preliminary item bank for physical function assuming four subdomains.


METHODS
Data from seven samples (N=17,726) using 136 items from nine questionnaires were evaluated. A generalized partial credit model was used to estimate item parameters, which were normed to a mean of 50 (SD=10) in the US population. Item bank properties were evaluated through Computerized Adaptive Test (CAT) simulations.


RESULTS
IRT requirements were fulfilled by 70 items covering activities of daily living, lower extremity, and central body functions. The original item context partly affected parameter stability. Items on upper body function, and need for aid or devices did not fit the IRT model. In simulations, a 10-item CAT eliminated floor and decreased ceiling effects, achieving a small standard error (< 2.2) across scores from 20 to 50 (reliability >0.95 for a representative US sample). This precision was not achieved over a similar range by any comparable fixed length item sets.


CONCLUSIONS
The methods of the PROMIS project are likely to substantially improve measures of physical function and to increase the efficiency of their administration using CAT.
Rose
M
M
Health Assessment Lab and QualityMetric Incorporated, 275 Wyman Street, Waltham, MA 02451, USA. mrose@hal-health.org
Bjorner
J B
JB
Becker
J
J
Fries
J F
JF
Ware
J E
JE
D000203:Activities of Daily Living; D003430:Cross-Sectional Studies; D003627:Data Interpretation, Statistical; D004185:Disability Evaluation; D005260:Female; D006304:Health Status; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D010003:Osteoarthritis / Q000503:physiopathology / Q000534:rehabilitation; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011795:Surveys and Questionnaires