Psychometric properties of the PROMIS Physical Function item bank in patients receiving physical therapy.

Martine H P Crins,Philip J Van Der Wees,Thomas Klausch,Caroline B Terwee,Leo D Roorda,Simone A Van Dulmen,Jacobus P Van Wouwe

doi:10.1371/journal.pone.0192187

Abstract

ObjectivesThe Patient-Reported Outcomes Measurement Information System (PROMIS) is a universally applicable set of instruments, including item banks, short forms and computer adaptive tests (CATs), measuring patient-reported health across different patient populations. PROMIS CATs are highly efficient and the use in practice is considered feasible with little administration time, offering standardized and routine patient monitoring. Before an item bank can be used as CAT, the psychometric properties of the item bank have to be examined. Therefore, the objective was to assess the psychometric properties of the Dutch-Flemish PROMIS Physical Function item bank (DF-PROMIS-PF) in Dutch patients receiving physical therapy.DesignCross-sectional study.Setting and participants805 patients >18 years, who received any kind of physical therapy in primary care in the past year, completed the full DF-PROMIS-PF (121 items).MethodsUnidimensionality was examined by Confirmatory Factor Analysis and local dependence and monotonicity were evaluated. A Graded Response Model was fitted. Construct validity was examined with correlations between DF-PROMIS-PF T-scores and scores on two legacy instruments (SF-36 Health Survey Physical Functioning scale [SF36-PF10] and the Health Assessment Questionnaire Disability-Index [HAQ-DI]). Reliability (standard errors of theta) was assessed.ResultsThe results for unidimensionality were mixed (scaled CFI = 0.924, TLI = 0.923, RMSEA = 0.045, 1th factor explained 61.5% of variance). Some local dependence was found (8.2% of item pairs). The item bank showed a broad coverage of the physical function construct (threshold-parameters range: -4.28–2.33) and good construct validity (correlation with SF36-PF10 = 0.84 and HAQ-DI = -0.85). Furthermore, the DF-PROMIS-PF showed greater reliability over a broader score-range than the SF36-PF10 and HAQ-DI.ConclusionsThe psychometric properties of the DF-PROMIS-PF item bank are sufficient. The DF-PROMIS-PF can now be used as short forms or CAT to measure the level of physical function of physiotherapy patients.

Highlights

Patient Reported Outcome Measures (PROMs) have become standard instruments to measure patients’ perceived health, and are used to assist in patient-physician shared-decision making and to monitor patients’ health over time
The item bank showed a broad coverage of the physical function construct and good construct validity
The DF-Patient-Reported Outcomes Measurement Information System (PROMIS)-PF can be used as short forms or computer adaptive tests (CATs) to measure the level of physical function of physiotherapy patients

Summary

Introduction

Patient Reported Outcome Measures (PROMs) have become standard instruments to measure patients’ perceived health, and are used to assist in patient-physician shared-decision making and to monitor patients’ health over time. PROMIS instruments are developed using Item Response Theory (IRT) and consist of item banks. These item banks (a set of items [questions] measuring one common construct) can be applied as short forms (fixed length subsets of items out of the item bank) or highly efficient computer adaptive tests (CAT). PROMIS tools are, if applied as short form or CAT, relatively short and the administration time is much less compared to traditional PROMs. the CAT application results in estimates with a low measurement error [7]. PROMIS instruments are easy to interpret, are less burdensome, have less measurement error, and have better content validity than traditional PROMs [7,8,9]

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Conclusion