Study Design. Patient-reported outcomes provide vital information when assessing effectiveness of clinical care. Yet, most patient-reported outcome instruments are limited by lack of validation and reliability to measure PF adequately. As part of the Patient-Reported Outcomes Measurement Information System (PROMIS), a PF item bank consisting of 124 items has been developed.
Objective. There is validation evidence for the PROMIS PF item bank in the general orthopedic patient population in general, but has yet to be validated in the patient with spinal disorders. This study aims to evaluate the psychometric properties of the PROMIS PF item bank specifically for patients presenting with spine-related complaints.
Summary of Background Data. Data were collected from adult patients visiting a university spine clinic for back and neck problems. All patients older than 18 years were eligible to participate. A total of 438 patients (49% male) were enrolled in this prospective study. Patients were 18- to 89-year old and presented with back problems (n = 286) and neck problems (n = 152). All patients were administered a 131 item questionnaire.
Methods. Conventional descriptive statistics such as means, standard deviations, and proportions were conducted to examine patient characteristics. A Rasch model was used to examine the psychometric properties of the instrument including dimensionality, floor/ceiling effects, reliabilities, and item bias.
Results. Results showed that a single PF dimension was supported by the data (i.e., unexplained variance was 2.9%). The instrument had 1.7% ceiling effect and 0.2% floor effect. Item reliability was 1.00 and person reliability was 0.99. We found evidence of item response bias associated with sex, age, and education in some items.
Conclusion. The PROMIS PF item bank adequately addressed outcomes of patients with spinal disorders as reliabilities were excellent, minimal ceiling/floor effect existed, and item bias was limited. Future effort should be focused on eliminating, rescaling, or modifying those items that had item bias.
Level of Evidence: 2
The purpose of this study is to evaluate the psychometric properties of the Patient-Reported Outcomes Measurement Information System (PROMIS) physical function (PF) item bank for patients. Results indicated the PROMIS PF item bank adequately addressed outcomes of patients with spinal disorders as reliabilities were excellent, ceiling/floor effects were minimal, and item bias was limited.
*University of Utah School of Medicine, Salt Lake City, UT
†University of Utah College of Engineering, Salt Lake City, UT; and
‡University of Utah College of Education, Salt Lake City, UT.
Address correspondence and reprint requests to Man Hung, PhD, Department of Orthopaedic Surgery Operations, University of Utah School of Medicine, 590 Wakara Way, Salt Lake City, UT 84108; E-mail: Man.Hung@hsc.utah.edu
Acknowledgment date: June 27, 2013. Revision date: October 14, 2013. Acceptance date: October 21, 2013.
The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication.
No funds were received in support of this work.
Relevant financial activities outside the submitted work: board membership, royalties, stock/stock options, and grants/grants pending.