The English and Chinese language versions of the Short Form 12-item Health Survey are equivalent

Background The Short Form 12-item Health Survey (SF-12v2) was originally developed in English, but it is also available in Hong Kong (HK) Chinese. While both language versions had their measurement properties well assessed in their respective populations, their measurement invariance in scores has not been examined. Therefore, we aimed to assess their measurement invariance. Methods We conducted a cross-sectional study on individuals aged 18 years or older at a university campus. Those who were bilingual in English and Chinese were randomly assigned to self-complete either the standard English or the HK Chinese SF-12v2. Measurement invariance of the two components and eight scales of the SF-12v2 was concluded if the corresponding 90% confidence interval (CI) for the difference between the two language versions entirely fell within the minimal clinically important difference of ± 3 units. Multiple-group confirmatory factor analysis (CFA) was also performed. Results A total of 1013 participants completed the SF-12v2 (496 in English and 517 in HK Chinese), with a mean age of 22 years (Range 18–58), and 626 participants (62%) were female. There were no significant differences in demographics. Only the physical and mental components and the mental health (MH) scale had their 90% CIs (0.21 to 1.61, − 1.00 to 0.98, and − 0.86 to 2.84, respectively) completely fall within the ± 3 units. The multiple-group CFA showed partial strict invariance. Conclusions The English and HK Chinese versions of the SF-12v2 can be used in studies with their two components and MH scores pooled in the analysis.