title: The challenge of measuring intra-individual change in fatigue during cancer treatment.
abstract: To evaluate how well three different patient-reported outcomes (PROs) measure individual change.
  
  
  
  Two hundred and fourteen patients (from two sites) initiating first or new chemotherapy for any stage of breast or gastrointestinal cancer participated. The 13-item FACIT Fatigue scale, a 7-item PROMIS®Fatigue Short Form (PROMIS 7a), and the PROMIS®Fatigue computer adaptive test (CAT) were administered monthly online for 6 months. Reliability of measured change was defined, under a population mixed effects model, as the ratio of estimated systematic variance in rate of change to the estimated total variance of measured individual differences in rate of change. Precision of individual measured change, the standard error of measurement of change, was given by the square root of the rate-of-change sampling variance. Linear and quadratic models were examined up to 3 and up to 6 months.
  
  
  
  A linear model for measured change showed the following by 6 and 3 months, respectively: PROMIS CAT (0.363 and 0.342); PROMIS SF (0.408 and 0.533); FACIT (0.459 and 0.473). Quadratic models offered no noteworthy improvement over linear models. Both reliability and precision results demonstrate the need to improve the measurement of intra-individual change.
  
  
  
  These results illustrate the challenge of reliably measuring individual change in fatigue with a level of confidence required for intervention. Optimizing clinically useful measurement of intra-individual differences over time continues to pose a challenge for PROs.
authors.affiliation: Public Health Sciences Division, Fred Hutchinson Cancer Research Center [Emerita], Seattle, WA, USA. cmoinpou@fredhutch.org.
authors.forename: Carol M
authors.initials: CM
authors.lastname: Moinpour
authors.affiliation: Pain Research Center, Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA.
authors.forename: Gary W
authors.initials: GW
authors.lastname: Donaldson
authors.affiliation: Health Services Research, Georgetown University Medical Center, and Georgetown University Lombardi Comprehensive Cancer Center, Washington, DC, USA.
authors.forename: Kimberly M
authors.initials: KM
authors.lastname: Davis
authors.affiliation: Health Services Research, Georgetown University Medical Center, and Georgetown University Lombardi Comprehensive Cancer Center, Washington, DC, USA.
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Potosky
authors.affiliation: Health Services Research, Georgetown University Medical Center, and Georgetown University Lombardi Comprehensive Cancer Center, Washington, DC, USA.
authors.forename: Roxanne E
authors.initials: RE
authors.lastname: Jensen
authors.affiliation: Seattle Cancer Care Alliance, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
authors.forename: Julie R
authors.initials: JR
authors.lastname: Gralow
authors.affiliation: Seattle Cancer Care Alliance, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Back
authors.affiliation: Hematology/Oncology, Levine Cancer Institute, Carolinas HealthCare System, Charlotte, NC, USA.
authors.forename: Jimmy J
authors.initials: JJ
authors.lastname: Hwang
authors.affiliation: Cancer Prevention Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
authors.forename: Jihye
authors.initials: J
authors.lastname: Yoon
authors.affiliation: Seattle Cancer Care Alliance, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
authors.forename: Debra L
authors.initials: DL
authors.lastname: Bernard
authors.affiliation: The Cystic Fibrosis Foundation, Bethesda, MD, USA.
authors.forename: Deena R
authors.initials: DR
authors.lastname: Loeffler
authors.affiliation: Department of Medical Social Sciences and Center for Patient-Centered Outcomes, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: Nan E
authors.initials: NE
authors.lastname: Rothrock
authors.affiliation: Departments of Medicine and Health Services Research, University of California Los Angeles, Los Angeles, CA, USA.
authors.forename: Ron D
authors.initials: RD
authors.lastname: Hays
authors.affiliation: Department of Health Policy and Management, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Bryce B
authors.initials: BB
authors.lastname: Reeve
authors.affiliation: Outcomes Research Branch, National Cancer Institute, Bethesda, MD, USA.
authors.forename: Ashley Wilder
authors.initials: AW
authors.lastname: Smith
authors.affiliation: Department of Medical Social Sciences and Center for Patient-Centered Outcomes, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Hahn
authors.affiliation: Department of Medical Social Sciences and Center for Patient-Centered Outcomes, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: David
authors.initials: D
authors.lastname: Cella
mesh_terms: D005221:Fatigue / Q000523:psychology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications*; D000071066:Patient Reported Outcome Measures; D011788:Quality of Life / Q000523:psychology*; D011795:Surveys and Questionnaires
keywords: Cancer; Fatigue; Intra-individual change; Measured change; Patient-reported outcomes