EQ-5D-3L and quality of life in total knee arthroplasty (TKA) patients: beyond the index scores

BACKGROUND: Many patient reported outcome measures (PROMs) generate single number index scores that summarise responses to different questions within a questionnaire. Although these are valuable as unambiguous indicators of ill-health and changes in health, further information can be gained from examining the questionnaire responses themselves. This has additional importance since the patients’ reports are those responses and not the index scores. This paper reanalyses data from two prospective multicentre clinical studies assessing patients’ quality of life before and after total knee arthroplasty (TKA) using the EQ-5D-3L. Patients who completed EQ-5D-3L questionnaires at 3 time periods were included from 4 countries (USA, UK, Australia, New Zealand) operated on by the same surgeons using two different knee replacement systems. Descriptive analyses included levels within EQ-5D dimensions and profiles (combinations of dimensions and levels) at baseline and follow-up, including changes over time and differences between implants. Regression analysis quantified the relationship between the profiles and the EQ VAS. RESULTS: Problems with mobility, usual activities and pain & discomfort, in that order, were most frequent for pre-operative patients. There were large improvements in every dimension after surgery, but the time that this was observed differed: for mobility, self-care and anxiety & depression, most of the improvement occurred during the first 10 months; for usual activities and pain & discomfort, over 11–22 months. Analysing profiles, 85% of patients experienced an unequivocal improvement, 5.9% had no change, 3.5% worsened and 5.5% a mixed change at 11–22 months follow-up. Anxiety & depression had the greatest impact on EQ VAS scores; while mobility and usual activities were also important; usual activities was particularly important post-surgery. CONCLUSIONS: The value of analysing patients’ responses to PROMs questionnaires without using summary scores was confirmed. The results add further detail to existing knowledge about the health problems that TKA patients experience before surgery, improvements after surgery, residual problems that some have, and the time at which improvements are experienced. This was a small study, but its methods may be easily replicated in other studies that use the EQ-5D-3L. It may also be possible to adapt them for other PROMs. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s41687-022-00497-0.