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Glossary

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A

Assessment Center

The Assessment Center is an online research management tool that enables researchers to create study–specific Web sites that securely capture patient data. Studies can include measures from the Assessment Center library, as well as custom instruments created or entered by the researcher. Assessment Center features include customization of items or instruments, such as format, randomization, and skip patterns; scoring of short forms and computerized–adaptive tests (CATs); storage of protected health information in a separate, secure database; automated accrual reports; data export; graphs of scores; and the ability to capture endorsement of online consent forms.

C

Computerized Adaptive Testing (CAT)

A flexible, computer–driven assessment that can use any items in the item bank to measure each domain. CAT selects only those items that sharpen the estimate of a respondent’s score on the domain being measured. CAT length varies but usually includes four to seven items.*

D

Domain

The trait or conceptual area that represents an instrument’s content. In item response theory, a domain is unidimensional, measuring a single trait or concept. It can be a symptom (such as pain) or a functional capability (physical function). A domain can also be divided into several related traits, concepts, or constructs labeled as ‘subdomains.’ For instance, the domain of pain is separated into the subdomains of pain interference and pain behavior, each of which possesses its own item bank, while fatigue is a domain that is not separated into any subdomains. This is decided empirically through the analysis of data collected under the domain and subdomain headings.*

I

Instrument

A measure, survey, or questionnaire. In PROMIS, this can be a short form, profile, or CAT.*

Item

A question or statement (and its response choices) in a survey.*

Item Bank

A collection of carefully selected items that provide an operational definition of a trait or construct.2, 3 A good item bank covers the entire continuum of the latent trait being measured, capturing different severity levels along the continuum.4 A well–calibrated item bank makes it possible to compare the amount of a given trait for individuals who complete different sets of items in the bank. Not only does this allow for ‘adaptive’ testing, because all items are calibrated onto one common scale, it is possible to compare scores across diverse groups of patients and item sets. A well-organized item bank with wide-ranging item difficulties can also enable the creation of a wide variety of short forms, depending on the target populations and purpose of assessment. At a given difficulty level, any chosen item should provide the maximum amount of information to estimate an individual’s score on the domain of interest.*

Item Response Theory (IRT)

A family of latent trait modeling in which a latent trait is an unobservable latent dimension that is thought to give rise to a set of observed item responses. Each item can be compared to other items measuring the same trait. Items that measure the same construct can be aggregated into longer assessments. IRT offers a framework for evaluating an assessment’s effectiveness, as well as evaluating the effectiveness of individual items within the assessment. IRT differs from classic test theory (CTT) in its assumptions about reliability and validity.

The reliability for an IRT-based measure is calculated based on each respondent’s ‘ability’ and varies across the continuum; in CTT, instrument reliability remains the same regardless of respondent ‘ability.’ For IRT-based instruments, validity is assessed across the entire item bank, and any instrument created from the item bank inherits this validity; for CTT instruments, validity is based on the individual instrument and must be reassessed if an instrument is modified in any way.*

P

PROMIS Network

A network of NIH–funded primary research sites and coordinating centers working collaboratively to develop a series of dynamic tools to reliably and validly measure patient–reported outcomes (PROs).

S

Self-Reported Health

Self-reported health is overall health and aspects of health that adults or children sense and are able to communicate to others: including global reports of health, functioning or wellbeing as well as specific types of abilities and symptoms. These may not refer to the ultimate causes of the perceived health (such as motor neuron functioning, blood sugar levels, etc.) as the unaided human senses, often, cannot perceive these.

T

The PROMIS Network Center (PNC)

An NIH–funded grant which facilitates the development of the PROMIS Strategic Plan and Research Agenda (SPRA) and implements this plan through management, coordination, and the provision of scientific consultation regarding PRO research design and analysis. The PNC is responsible for leveraging PROMIS as a public good through communications, dissemination and business development functions with a focus on supporting the long–term viability and sustainability of the PROMIS^® Network.

The PROMIS Statistical Center (PSC)

An NIH-funded grant which advises and educates PROMIS Research Sites on a range of qualitative and quantitative research methods, develops and implements processes to ensure data quality; provides leadership in the development of PROMIS approved translations of new and extant domains; assists in the development and implementation of protocols; provides consultation on research design, sample size, sampling plans and power estimates for item bank testing; provides psychometric and statistical support for the network; and works collaboratively with the PROMIS Network to create sustainability.

The PROMIS Technical Center (PTC)

An NIH–funded grant which provides and manages a secure, customizable data collection, management, and reporting system (Assessment Center); serve as a cost-effective, efficient technological resource for the PROMIS® Network; conduct outreach efforts through publications, presentations, and educational tools to increase the research community’s interest in the PROMIS® measures and Assessment Center as a platform for data collection.

Trait

Synonymous with the terms ‘construct’ and ‘concept.’*

* Originally published in the PROMIS Scoring Guide – Glossary, January 2011