Average and individual differences between the 12-item MOS Short-form Health Survey version 2 (SF-12 V.2) and the veterans RAND 12-item Health Survey (VR-12) in the Chinese population

Background The 12-item MOS Short-form Health Survey version 2 (SF-12v2) and the Veterans RAND 12-item Health Survey (VR-12) are generic health-related quality of life measures. They are fairly similar, but their differences in scores have not been assessed. Therefore, this study aimed to assess the differences between the SF-12v2 and the VR-12 in a Chinese population. Methods We conducted a household survey of 500 Chinese adults in Hong Kong. Both the SF-12v2 and the VR-12 were self-administered. The physical component summary score (PCS) and the mental component summary score (MCS) of each instrument were computed using well established algorithms. Their mean differences were assessed using 95% confidence interval (CI), and their individual differences were assessed by Bland-Altman analysis. Results The participants had a mean age of 38 years (range: 18-80 years). The mean PCS and MCS scores of the SF-12v2 were 50.3 (SD = 6.5) and 49.0 (SD = 9.0), while those of the VR-12 were 49.6 (SD = 6.2) and 49.7 (SD = 8.8), respectively. The corresponding paired differences (SF-12v2-VR-12) of the PCS and MCS were 0.8, 95% CI (0.4-1.1) and - 0.7, 95% CI (- 1.2 to - 0.2), respectively. All confidence limits fell within the minimal clinical important difference (MCID) of 3. The 95% limits of agreement were - 7.0, 8.5 for PCS and - 11.2, 9.9 for MCS, which fell outside the corresponding MCID for individual responses. Conclusion The SF-12v2 and the VR-12 reached mean equivalence at the group sample level, but there was a range of individual differences.