Measurement invariance of the Functional Assessment of Cancer Therapy-Colorectal quality-of-life instrument among modes of administration.
OBJECTIVE
To test for the measurement invariance of the Functional Assessment of Cancer Therapy-Colorectal (FACT-C) in patients with colorectal neoplasms between two modes of administration (self- and interviewer administrations). It is important to establish the measurement invariance of the FACT-C across different modes of administration to ascertain whether it is valid to pool FACT-C data collected by different modes or to assess each group separately.


METHODS
A cross-sectional sample of 391 Chinese patients with colorectal neoplasms was recruited from specialist outpatient clinics between September 2009 and July 2010. Confirmatory factor analysis (CFA) was used to test the original five-factor model of the FACT-C on data collected by self- and interviewer administrations in single-group analysis. Multiple-group CFA was then used to compare the factor structure between the two modes of administration using chi-square tests and other goodness-of-fit statistics.


RESULTS
The hypothesized five-factor model of FACT-C demonstrated good fit in each group. Configural invariance and metric invariance were fully supported in multiple-group CFA. Some item intercepts and their corresponding error variances were not identical between administration groups, suggesting evidence of partial strict factorial invariance.


CONCLUSIONS
Our results confirmed that the five-factor structure of FACT-C was invariant in Chinese patients using both self- and interviewer administrations. It is appropriate to pool or compare data in the emotional well-being and colorectal cancer subscale scores collected by both administrations. Measurement invariance in three items, one from each of the other subscales, may be contaminated by response bias between modes of administration.
Department of Family Medicine and Primary Care, The University of Hong Kong, 3/F, Ap Lei Chau Clinic, 161 Ap Lei Chau Main Street, Ap Lei Chau, Hong Kong Island, Hong Kong. carlosho@hku.hk
Carlos K H
CK
Wong
Cindy L K
CL
Lam
Brendan
B
Mulhern
Wai-Lun
WL
Law
Jensen T C
JT
Poon
Dora L W
DL
Kwong
Janice
J
Tsang
D000368:Aged; D000704:Analysis of Variance; D016009:Chi-Square Distribution; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000523:psychology*; D003430:Cross-Sectional Studies; D005163:Factor Analysis, Statistical; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D008875:Middle Aged; D011594:Psychometrics / Q000295:instrumentation*; D011788:Quality of Life; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D016896:Treatment Outcome