Longitudinal and dynamic measurement invariance of the FACIT-Fatigue scale: an application of the measurement model of derivatives to ECOG-ACRIN study E2805

Ryne Estabrook*, David Cella, Fengmin Zhao, Judith Manola, Robert S. DiPaola, Lynne I. Wagner, Naomi B. Haas

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose: While quality of life measures may be used to assess meaningful change and group differences, their scaling and validation often rely on a single occasion of measurement. Using the 13-item FACIT-Fatigue questionnaire at three timepoints, this study tests whether individual items change together in ways consistent with a general fatigue factor. Methods: The measurement model of derivatives (MMOD) is a novel method for measurement evaluation that directly assesses whether a given factor structure accurately describes how individual test items change over time. MMOD transforms item-level longitudinal data into a set of orthogonal change scores, each one representing either a within-person longitudinal mean or a different type of longitudinal change. These change scores are then factor analyzed and tested for invariance. This approach is applied to the FACIT-Fatigue scale in a sample of patients with renal cell carcinoma treated on ’ECOG-ACRIN Cancer Research Group (ECOG-ACRIN) study 2805. Results: Analyses revealed strong evidence of unidimensionality, and apparent factorial invariance using traditional techniques. MMOD revealed a small but statistically significant difference in factor structure (χ122=49.597, p<. 001), where factor loadings were weaker and more variable for measuring longitudinal change. Conclusions: The differences in factor structure were not large enough to substantially affect scale usage in this application, but they do reveal some variability across items in the FACIT-Fatigue in their ability to detect change. Future applications should consider differential sensitivity of individual items in multi-item scales, and perhaps even capitalize upon these differences by selecting items that are more sensitive to change.

Original languageEnglish (US)
Pages (from-to)1589-1597
Number of pages9
JournalQuality of Life Research
Volume27
Issue number6
DOIs
StatePublished - Jun 1 2018

Keywords

  • Factor analysis
  • Fatigue
  • Longitudinal modeling
  • Measurement invariance

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health

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