Introduction
What is new?
- •
This article describes the development of a comprehensive physical function (PF) item bank. This item bank can improve the measurement of PF by standardizing the metric and enabling short and precise computerized adaptive test assessment through readily available software, thus facilitating the use of patient self-assessment in clinical practice and research.
Measurement of patient-reported outcomes (PROs) in clinical studies has steadily increased in frequency, as has its importance in evaluating therapies and developing treatment plans. The plethora of outcomes tools available today allows for increasing the specificity of measurement over a wide range of domains. However, most widely used PRO tools have well-described shortcomings, including high respondent burden and lack of measurement precision. Moreover, results from different instruments can be hard to compare, which limits the interpretability of PRO data.
To address these shortcomings, the National Institutes of Health funded an initiative to build a comprehensive Patient-Reported Outcomes Measurement Information System (PROMIS) [1], [2]. The PROMIS uses item response theory (IRT) and computerized adaptive tests (CATs), which are believed to be promising solutions to the most important limitations of current measurement tools. An IRT item bank consists of a set of items measuring the same construct and parameters that describe the items' measurement properties [3]. Item banks provide the foundation for CATs, which make it possible to administer the most informative items to an individual respondent [4]. Thus, higher precision can be achieved, while respondent burden can be reduced [5], [6], [7].
One aim of the PROMIS initiative was to build an improved item bank for the Physical Function (PF) construct, which has been evaluated using IRT methods for more than a decade [8], [9], [10], [11], [12]. Items covering a wide range of functioning, from self-care to strenuous activities, have been calibrated using IRT models, and some of the first CATs were developed for PF construct [13], [14]. We presented results from a rigorous evaluation of IRT methods in preparation for development of the PROMIS PF item bank earlier in this journal [6]. The current article reports on the development and initial psychometric evaluation of the PROMIS PF item bank.