How item banks and their application can influence measurement practice in rehabilitation medicine: a PROMIS fatigue item bank example

Abstract

Objective: To illustrate how measurement practices can be advanced by using as an example the fatigue item bank (FIB) and its applications (short forms and computerized adaptive testing [CAT]) that were developed through the National Institutes of Health Patient Reported Outcomes Measurement Information System (PROMIS) Cooperative Group.

Design: Psychometric analysis of data collected by an Internet survey company using item response theory-related techniques.

Setting: A U.S. general population representative sample collected through the Internet.

Participants: Respondents used for dimensionality evaluation of the PROMIS FIB (N=603) and item calibrations (N=14,931).

Interventions: Not applicable.

Main outcome measures: Fatigue items (112) developed by the PROMIS fatigue domain working group, 13-item Functional Assessment of Chronic Illness Therapy-Fatigue, and 4-item Medical Outcomes Study 36-Item Short Form Health Survey Vitality scale.

Results: The PROMIS FIB version 1, which consists of 95 items, showed acceptable psychometric properties. CAT showed consistently better precision than short forms. However, all 3 short forms showed good precision for most participants in that more than 95% of the sample could be measured precisely with reliability greater than 0.9.

Conclusions: Measurement practice can be advanced by using a psychometrically sound measurement tool and its applications. This example shows that CAT and short forms derived from the PROMIS FIB can reliably estimate fatigue reported by the U.S. general population. Evaluation in clinical populations is warranted before the item bank can be used for clinical trials.

Copyright © 2011 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Hypothesized Model Used for Bi-factor Analysis NOTE:

1. General factor is defined as “overall fatigue” and two local factors are “fatigue impact” and “fatigue experience”.

2. IMP item-n: items measure “fatigue impact”

3. EXP item-n: items measure “fatigue experience”

4. CFI=0.911; TLI=0.996; RMSEA=0.100

Figure 2

Figure 3

Comparisons of Short-forms and CAT

Figure 4

Distribution of the Sample Fatigue Scores (in T-score).