Item response theory, computerized adaptive testing, and PROMIS: assessment of physical function.
OBJECTIVE
Patient-reported outcome (PRO) questionnaires record health information directly from research participants because observers may not accurately represent the patient perspective. Patient-reported Outcomes Measurement Information System (PROMIS) is a US National Institutes of Health cooperative group charged with bringing PRO to a new level of precision and standardization across diseases by item development and use of item response theory (IRT).


METHODS
With IRT methods, improved items are calibrated on an underlying concept to form an item bank for a "domain" such as physical function (PF). The most informative items can be combined to construct efficient "instruments" such as 10-item or 20-item PF static forms. Each item is calibrated on the basis of the probability that a given person will respond at a given level, and the ability of the item to discriminate people from one another. Tailored forms may cover any desired level of the domain being measured. Computerized adaptive testing (CAT) selects the best items to sharpen the estimate of a person's functional ability, based on prior responses to earlier questions. PROMIS item banks have been improved with experience from several thousand items, and are calibrated on over 21,000 respondents.


RESULTS
In areas tested to date, PROMIS PF instruments are superior or equal to Health Assessment Questionnaire and Medical Outcome Study Short Form-36 Survey legacy instruments in clarity, translatability, patient importance, reliability, and sensitivity to change.


CONCLUSIONS
Precise measures, such as PROMIS, efficiently incorporate patient self-report of health into research, potentially reducing research cost by lowering sample size requirements. The advent of routine IRT applications has the potential to transform PRO measurement.
From the Department of Medicine, Stanford University School of Medicine, Stanford, California; National Institutes of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), Bethesda, Maryland, USA; Medical School Charité, University Medicine Berlin, Berlin, Germany; Department of Medical Social Sciences, Feinberg School of Medicine, Northwestern University, Chicago, Illinois; Department of Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan; Department of Pediatrics, University of Cincinnati School of Medicine, Cincinnati, Ohio, USA.
James F
JF
Fries
James
J
Witter
Matthias
M
Rose
David
D
Cella
Dinesh
D
Khanna
Esi
E
Morgan-DeWitt
D000203:Activities of Daily Living; D004185:Disability Evaluation; D006801:Humans; D017063:Outcome Assessment, Health Care / Q000379:methods*; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D057566:Self Report; D011795:Surveys and Questionnaires
COMPUTERIZED ADAPTIVE TESTING; DISABILITY; ITEM RESPONSE THEORY; PHYSICAL FUNCTION; PROMIS