The Singaporean English and Chinese versions of the EQ-5D achieved measurement equivalence in cancer patients.
OBJECTIVE
To assess measurement equivalence of the Singaporean English and Chinese versions of the EuroQol Group's 5-domain questionnaire (EQ-5D) in cancer patients.


METHODS
Seven hundred and seventy-one ethnic Chinese patients in Singapore were recruited, and they answered either an English or a Chinese version of the EQ-5D. Seven days later, a similar questionnaire in the same language was mailed to the patients. Regression analysis was used to assess equivalence of the mean values obtained by using the two language versions. The validity, responsiveness to change, and reliability of the two versions of the EQ-5D were assessed and compared.


RESULTS
Based on the prespecified equivalence margin of +/-10% for binary outcome, +/-0.05 for utility index, and +/-5 points in the visual analog scale, the two language versions of the EQ-5D gave equivalent mean values at item and scale levels. They also showed similar characteristics in validity, responsiveness, and reliability. For example, the test-retest reliability values for the EQ-5D utility index in the two language samples were identical in two significant digits: 0.79.


CONCLUSIONS
The Singaporean English and Chinese versions of the EQ-5D were validated in cancer patients and were shown to achieve measurement equivalence.
Gao
Fei
F
Division of Clinical Trials and Epidemiological Sciences, National Cancer Centre, 11 Hospital Drive, Singapore 169610, Singapore. ctegfe@nccs.com.sg
Ng
Gim-Yew
GY
Cheung
Yin-Bun
YB
Thumboo
Julian
J
Pang
Grace
G
Koo
Wen-Hsin
WH
Sethi
Vijay-Kumar
VK
Wee
Joseph
J
Goh
Cynthia
C
D000328:Adult; D044466:Asian People / Q000208:ethnology; D003144:Communication Barriers; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000523:psychology*; D011594:Psychometrics / Q000379:methods; D011788:Quality of Life / Q000523:psychology*; D015203:Reproducibility of Results; D012846:Singapore; D011795:Surveys and Questionnaires / Q000592:standards*