VOL. 86-B, No. 6, AUGUST 2004 801 Patient-reported outcome in total hip replacement A COMPARISON OF FIVE INSTRUMENTS OF HEALTH STATUS M. Ostendorf, H. F. van Stel, E. Buskens, A. J. P. Schrijvers, L. N. Marting, A. J. Verbout, W. J. A. Dhert From the University Medical Center, Utrecht, The Netherlands  M. Ostendorf, MSc, PhD, Student  A. J. Verbout, MD, PhD, Professor, Orthopaedic Surgeon  W. J. A. Dhert, MD, PhD, Director of Orthopaedic Research Department of Orthopaedics, University Medical Center, P O Box 85500, 3508 GA, Utrecht, The Netherlands.  H. F. van Stel, PhD, Clinical Epidemiologist  E. Buskens, MD, PhD, Clinical Epidemiologist  A. J. P. Schrijvers, PhD, Professor of Health Services Julius Centre for Health Sciences and Primary Care, University Medical Center, PO Box 85500, 3508 GA, Utrecht, The Netherlands.  L. N. Marting, MD Department of Orthopaedics, Sint Antonius Hospital, PO Box 2500, 3430 Nieuwegein, The Netherlands. Correspondence should be sent to Dr M. Ostendorf. ©2004 British Editorial Society of Bone and Joint Surgery doi:10.1302/0301-620X.86B6. 14950 $2.00 J Bone Joint Surg [Br] 2004;86-B:801-8. Received 11 September 2003; Accepted 4 November 2003 Our aim was to define the minimum set of patient-reported outcome measures which are required to assess health status after total hip replacement (THR). In 114 patients, we compared the pre-operative characteristics and sensitivity to change of the Oxford hip score (OHS), the Western Ontario and McMaster Universities osteoarthritis index (WOMAC), the SF-36, the SF-12 (derived from the SF-36), and the Euroqol questionnaire (EQ-5D). At one year after operation, very large effect sizes were found for the disease-specific measures, the physical domains of the SF-12, SF-36 and the EQ-5D index (1.3 to 3.0). Patients in Charnley class A showed more change in the OHS, WOMAC pain and function, the physical domains of the SF-36 and the EQ-5D vas (p < 0.05) compared with those in the Charnley B and C group. In this group, the effect size for the OHS more than doubled the effect sizes of WOMAC pain and physical function. We found high correlations and correlations of change between the OHS, the WOMAC, the physical domains of the SF-12 and the SF-36 and EQ-5D index . The SF-36 and EQ-5D scores at one year after operation approached those of the general population. Furthermore, we found a binomial distribution of the pre-operative EQ-5D index score and a pre-operative discrepancy and post-operative agreement between the EQ-5D vas and EQ-5D index . We recommend the use of the OHS and SF-12 in the assessment of THR. The SF-36 may be used in circumstances when smaller changes in health status are investigated, for example in the follow-up of THR. The EQ-5D is useful in situations in which utility values are needed in order to calculate cost-effectiveness or quality-adjusted life years (QALYs), such as in the assessment of new techniques in THR. Total hip replacement (THR) is an effective treatment which improves function and relieves pain in the hip secondary to severe osteoarthritis or other diseases which affect the joint. 1 In an environment of limited resources, health-status questionnaires are of particular importance when comparing the cost-to-bene- fit ratio of medical interventions. 2 In the evalu- ation of THR, the Western Ontario and McMaster Universities osteoarthritis index (WOMAC) and the SF-36 health status ques- tionnaire (SF-36) have been especially recom- mended as patient-centred questionnaires. 3 However, the 12-item Oxford hip score (OHS) and the Euroqol questionnaire have also been suggested, the first because of its brevity and site-specificity and the second because it allows comparisons to be made with the effect of other health-care interventions. 4,5 The psycho- metric characteristics of these four question- naires have been reported extensively in the literature. Our aim was to define a minimum set of outcome measures to assess health status in THR. We therefore compared the baseline characterics and sensitivity to change of the OHS, the WOMAC, the SF-36, the SF-12 health status questionnaire (SF-12) which is derived from the SF-36 and the Euroqol ques- tionnaire (EQ-5D). We also investigated the pre- and post-operative distribution of the Euroqol scores. Finally, the SF-36 and Euroqol scores were compared with published data on age and gender-matched norms (personal com- munication). 6,7 Patients and Methods Between April 1999 and September 2000, 147 patients were recruited from three different hospitals, one university hospital and two regional hospitals. They were asked to partici- pate in the study after their orthopaedic sur- geon had put them on the waiting list for primary total hip replacement. Patients were excluded from the study if they were under the