Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement
Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.
Developing an Improved PROMIS Fatigue Short-Form for Use in Patients with Fibromyalgia.
Schilling5, Stephen, Blum1, Steven I., Tourkodimitris2, Stavros, Stankus3, Andy, Williams4, David A.
The NIH roadmap project "Patient-Reported Outcomes Measurement Information System (PROMIS)" has developed calibrated item banks for a variety of domains relevant to chronic illnesses, including fatigue, which can be used to administer computer adaptive testing or to develop static questionnaires and short forms. PROMIS has developed a 7-item Short-Form for general use in fatigue, but it is unclear how well this short-form performs in measuring the fatigue of individuals with Fibromyalgia (FM). This study sought to develop and test an improved fatigue short-form for use in FM patients, constructed from the PROMIS fatigue item bank using calibrations derived from individuals with FM.
An Item Response Theory (IRT) analysis was conducted using data collected from an internet-based survey of 1207 self-identified individuals (88.9% Female; 90.5% Caucasian) currently suffering from FM. Participants had to be >= 18 years at the time of response and have been previously diagnosed with FM by a physician. In order to reduce response burden, respondents were randomized into one of 3 cohorts, each of which completed one-third of the 95 items from the entire PROMIS v1.0 Fatigue Item Bank (www.nihpromis.org). Items were balanced between cohorts so that there was no overlap of questions. IRT analysis was conducted using Samejima's Graded Response Model (GRM) to fit the data using MULTILOG 7. The relative contribution of items measuring the latent trait was assessed by the item information function (IIF). Polyserial Correlations and the average of the IIF for all items from the full item bank were compared with those items included in the PROMIS Fatigue-Short Form to identify candidate items for an alternative scale. Cronbach's alpha was used to assess the reliability of the existing and proposed alternative scales.
The current 7-item PROMIS Fatigue Short-Form contains 3 Fatigue Experience items and 4 Fatigue Impact Items. The Fatigue Experience items had a Cronbach's alpha reliability score of 0.77. The Fatigue Impact items had a reliability score of 0.81; including one item [IMP40: How often did you have enough energy to exercise strenuously?] which had the lowest information function (IIF=0.11) in the full item-bank. By contrast, the items with the highest IIF from both Fatigue Experience [EXP40: How fatigued were you on average? (IIF=6.22)] and Fatigue Impact [IMP51: To what degree did you have trouble finishing things? (IIF=2.94)] are not included in the current PROMIS Short-Form. A proposed short-form containing items with high average IIFs for Fatigue Experience and Fatigue Impact, each containing 5 items achieved reliability scores of 0.95 and 0.92 respectively. It is likely that the concept of fatigue for individuals with FM differs to some degree from other clinical populations; this is reflected in the identification of a new set of items showing greater discriminative ability for measuring fatigue in FM patients.
A new Short-Form can provide improved precision in measurement of the fatigue associated with fibromyalgia compared with the current 7-item PROMIS Fatigue Short-Form. Further testing and validation of the alternative short-form is needed.
To cite this abstract, please use the following information:
Schilling, Stephen, Blum, Steven I., Tourkodimitris, Stavros, Stankus, Andy, Williams, David A.; Developing an Improved PROMIS Fatigue Short-Form for Use in Patients with Fibromyalgia. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :800