TY - JOUR
T1 - Longitudinal and dynamic measurement invariance of the FACIT-Fatigue scale
T2 - an application of the measurement model of derivatives to ECOG-ACRIN study E2805
AU - Estabrook, Ryne
AU - Cella, David
AU - Zhao, Fengmin
AU - Manola, Judith
AU - DiPaola, Robert S.
AU - Wagner, Lynne I.
AU - Haas, Naomi B.
N1 - Publisher Copyright:
© 2018, Springer International Publishing AG, part of Springer Nature.
PY - 2018/6/1
Y1 - 2018/6/1
N2 - 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.
AB - 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.
KW - Factor analysis
KW - Fatigue
KW - Longitudinal modeling
KW - Measurement invariance
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U2 - 10.1007/s11136-018-1817-4
DO - 10.1007/s11136-018-1817-4
M3 - Article
C2 - 29508208
AN - SCOPUS:85046904387
SN - 0962-9343
VL - 27
SP - 1589
EP - 1597
JO - Quality of Life Research
JF - Quality of Life Research
IS - 6
ER -