Equating EORTC QLQ-C30 and FACT-G scores and its use in oncological research.
OBJECTIVE
To investigate the equivalence of the European Organization for Research and Treatment of Cancer Core Questionnaire (EORTC QLQ-C30) and the Functional Assessment for Cancer Therapy-General (FACT-G) on the basis of corresponding subscales, and where appropriate to derive a scheme for converting QLQ-C30 scores into FACT-G scores and vice versa for use in oncological research.


METHODS
A calibration sample of 737 cancer patients (mean age 51.4+/-7.6 (SD), 63% female, 25% with current chemotherapy) who filled in both quality of life (QOL) questionnaires was used. Both classical test theory and the Rasch measurement model were applied.


RESULTS
Three of the four subscales common to both QOL instruments (physical, emotional, functional) proved suitable for equating (acceptable inter-correlations of corresponding subscales physical (r=0.77), emotional domain (r=0.60) role/functional (r=0.63) relative to their internal consistency, sufficient unidimensionality of pooled subscales, satisfactory fit to the Rasch model). Conversion tables for these subscales were generated.


CONCLUSIONS
The conversion tables developed in this study (physical, emotional and functional/role domain) appear promising for the comparison between EORTC QLQ-C30 and FACT-G scores of patient samples.
Holzner
B
B
Department of Psychiatry, Innsbruck University Hospital, Anichstr.35, A-6020 Innsbruck, Austria. Bernhard.Holzner@uklibk.ac.at
Bode
R K
RK
Hahn
E A
EA
Cella
D
D
Kopp
M
M
Sperner-Unterweger
B
B
Kemmler
G
G
D035843:Biomedical Research; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008495:Medical Oncology; D008875:Middle Aged; D009369:Neoplasms / Q000523:psychology*; D011788:Quality of Life; D011795:Surveys and Questionnaires / Q000592:standards*