PROMIS Physical Function Item Bank
Also known as: PROMIS PF Item Bank, PROMIS Physical Function Bank, Physical Function Item Bank, PROMIS Mobility Bank
The PROMIS Physical Function item bank is a large, item-response-theory-calibrated collection of self-reported questions about physical functioning and mobility, developed under the United States National Institutes of Health Patient-Reported Outcomes Measurement Information System initiative. Rather than being a fixed questionnaire, it is a bank of items all placed on a single underlying continuum, so that any subset of items measures the same construct on the same metric. Rose and colleagues' 2008 evaluation of the preliminary bank demonstrated the expected advantages of this approach, and Cella and colleagues' 2010 report described the calibration of PROMIS's first wave of adult item banks. The items are calibrated with a graded response model and anchored to a T-score metric with a mean of 50 and a standard deviation of 10 in the United States general population. Because every item sits on the common metric, the bank supports both fixed short forms and computerized adaptive testing, letting researchers and clinicians measure physical function precisely with relatively few questions and compare scores across studies and instruments.
Key highlights
- Places every item on a single T-score metric, so scores are comparable regardless of which items were administered.
- Supports both fixed short forms and computerized adaptive testing from one calibration, trading length against precision flexibly.
- Built on item response theory, it quantifies measurement precision at each level of function and targets items efficiently.
- Can be linked to legacy physical-function instruments, letting prior data be translated into the common PROMIS metric.
Intuition
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How it works
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When to use it
Use the PROMIS Physical Function item bank when you need to measure self-reported physical function or mobility precisely, flexibly, and comparably, whether in disability and rehabilitation research, clinical care, or outcome monitoring. It is ideal when you want short, low-burden assessment without losing the ability to compare scores across patients, studies, instruments, or time, and when a standardized, population-referenced metric is valuable. The bank suits both fixed short forms, where simplicity and equal administration matter, and computerized adaptive testing, where precision with minimal items is the priority. It is less appropriate when the construct of interest is not self-reported physical function — for instance, performance-based mobility tests or condition-specific symptoms — or when a population differs enough from the calibration sample that item parameters may not hold without checking for measurement invariance.
Strengths & limitations
- Places every item on a single T-score metric, so scores are comparable regardless of which items were administered.
- Supports both fixed short forms and computerized adaptive testing from one calibration, trading length against precision flexibly.
- Built on item response theory, it quantifies measurement precision at each level of function and targets items efficiently.
- Can be linked to legacy physical-function instruments, letting prior data be translated into the common PROMIS metric.
- Calibration depends on a large reference sample, and item parameters may not transfer cleanly to populations unlike the calibration group.
- It measures self-reported function only, which can diverge from performance-based assessment of what a person can actually do.
- The graded response model assumes unidimensionality and local independence, which can be strained when items tap distinct facets of mobility.
- Differential item functioning across groups must be checked, since uncorrected DIF can make T-scores non-comparable across populations.
Common pitfalls
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Applications
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Frequently asked
What does a PROMIS Physical Function T-score of 50 mean?
A T-score of 50 represents the average level of self-reported physical function in the United States general population, and each ten points corresponds to one standard deviation. So a score of 40 is one standard deviation below average, indicating more limitation, and 60 is one standard deviation above average, indicating better function. Because all items in the bank are calibrated to this same metric, the T-score has a fixed meaning regardless of which items a person answered, which is what makes scores comparable across patients, studies, and over time.
How can different people answer different items and still get comparable scores?
Through item response theory calibration. Every item in the bank is modeled in relation to the underlying physical-function continuum, with parameters describing how difficult and how discriminating it is. Once items are calibrated to the same scale, they become interchangeable rulers: a few easy items and a few hard items both locate a person on the same continuum. The scoring uses the calibrated parameters, not a raw sum, so a frail patient given easy items and a fit person given hard items receive directly comparable T-scores. This is the core advantage of an item bank over a fixed questionnaire.
Is the PROMIS Physical Function bank the same as a fixed PROMIS short form?
No. The bank is the full calibrated pool of items, while a short form is a specific fixed subset chosen from it. Both produce scores on the same T-score metric because they draw on the same calibration, but the bank also enables computerized adaptive testing, which selects items dynamically for each respondent. Short forms are convenient when everyone should answer the same items, whereas the full bank and CAT offer more precision and efficiency. Choosing among them is a trade-off between administrative simplicity and measurement precision, not a change in what is measured.
Sources
- 1.Rose, M., Bjorner, J. B., Becker, J., Fries, J. F., & Ware, J. E. (2008). Evaluation of a preliminary physical function item bank supported the expected advantages of the Patient-Reported Outcomes Measurement Information System (PROMIS). Journal of Clinical Epidemiology, 61(1), 17-33.
- 2.Cella, D., Riley, W., Stone, A., et al. (2010). The Patient-Reported Outcomes Measurement Information System (PROMIS) developed and tested its first wave of adult self-reported health outcome item banks: 2005-2008. Journal of Clinical Epidemiology, 63(11), 1179-1194.
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Cite this page
ScholarGate. (2026, June 23). PROMIS Physical Function Item Bank. ScholarGate. https://scholargate.app/disability-studies/promis-physical-function-bank