Table 3.

Comparative responsiveness and minimal important differences (MID) of health-related quality of life (HRQoL) instruments reported in previous studies

Authors	Country	No. of subjects	Measurement time intervals	Instrument*	Findings
Shi HY, et al. (present study)	Taiwan	67 revision THA	Preoperative and 6-month surveys	HHS, SF-36	HHS revealed greater overall responsiveness than the SF-36 between pre-op and 6-month surveys.
Soohoo NF, et al. (2007)[7]	U.S.	89 primary THA	Preoperative and 5 to 17-month surveys	WOMAC, SF-36	The standardized response means (SRM) for the WOMAC ranged from -0.93 to -1.49, and the effect size (ES) ranged from -1.02 to -1.53. The SRM for the SF-36 ranged from 0.22 to 1.64, and the ES ranged from 0.20 to 1.97.
Quintana JM, et al. (2005) [22]	Spain	310 primary THA	Preoperative, 6- and 24-month surveys	WOMAC, SF-36	WOMAC exhibited treatment responsiveness superior to the SF-36. The percentage of minimal detectable change (MDC) was higher than 80% for all WOMAC domains, except stiffness (60%), while it was higher than 40% in the physical domains of the SF-36 (physical function, physical role, or bodily pain).
Angst F, et al. (2001)[23]	Switzerland	433 hip or knee OA	Preoperative and 3-month surveys	WOMAC, SF-36	SRM = 0.723 for WOMAC and SRM = 0.528 for SF-36 at the end of rehabilitation; SRM = 0.377 for WOMAC and SRM = 0.468 for SF-36 at the three month follow up. In the measurement of function, the WOMAC was significantly more responsive than the SF-36 (SRMs, end of rehabilitation: 0.628 vs. 0.249; three month follow up: 0.235 vs. -0.001).
Hoeksma HL, et al. (2003) [24]	Netherlands	75 hip OA	Preoperative and 5-week surveys	HHS, SF-36	The responsiveness ratio for the HHS was high (1.70) compared with walking speed (0.45), pain during walking (0.66), and the subscales of the SF-36-"bodily pain" (0.42) and "physical functioning" (0.36).
Weigl M, et al. (2006)[25]	Germany	439 low (upper) back pain and conditions of the lower (upper) extremities patients	Preoperative and 2~4-week surveys	SCQ SF-36 NASS DASH	The condition-specific instruments demonstrated a good responsiveness with an ES ranging between 0.28 and 0.55 and with a SRM between 0.32 and 0.94. The responsiveness of the SF-36 Physical Function scale showed a lower responsiveness than the condition-specific scales.
Lübbeke A, et al. (2007) [26]	Switzerland	435 primary THA, 116 revision THA	Preoperative and 5-year surveys	HHS, WOMAC, SF-12	HHS and WOMAC were relatively more responsive for physical and pain functions than the SF-12.

*HHS = Harris Hip Score, SF-36 = Medical Outcomes Study Short Form-36 Health Survey, WOMAC = Western Ontario and McMaster Universities Osteoarthritis Index, SCQ = Self-administered Comorbidity Questionnaire, NASS = North American Spine Society Questionnaire, DASH = Disabilities of Arm, Shoulder, and Hand Questionnaire