Assessing responsiveness of the EQ-5D-3L, the Oxford Hip Score, and the Oxford Knee Score in the NHS patient-reported outcome measures

Abstract

Background: The degree to which a validated instrument is able to detect clinically significant change over time is an important issue for the better management of hip or knee replacement surgery. This study examines the internal responsiveness of the EQ-5D-3L, the Oxford Hip Score (OHS), and the Oxford Knee Score (OKS) by various methods. Data from NHS patient-reported outcome measures (PROMs) linked to the Hospital Episodes Statistics (HES) dataset (2009-2015) was analysed for patients who underwent primary hip surgery (N = 181,424) and primary knee surgery (N = 191,379).

Methods: Paired data-specific univariate responsiveness was investigated using the standardized response mean (SRM), the standardized effect size (SES), and the responsiveness index (RI). Multivariate responsiveness was furthermore examined using the defined capacity of benefit score (i.e. paired data-specific MCID), adjusting baseline covariates such as age, gender, and comorbidities in the Box-Cox regression models. The observed and predicted percentages of patient improvement were examined both as a whole and by the patients' self-assessed transition level.

Results: The results showed that both the OHS and the OKS demonstrated great univariate and multivariate responsiveness. The percentages of the observed (predicted) total improvement were high: 51 (54)% in the OHS and 73 (58)% in OKS. The OHS and the OKS showed distinctive differences in improvement by the 3-level transition, i.e. a little better vs. about the same vs. a little worse. The univariate responsiveness of the EQ-5D-3L showed moderate effects in total by Cohen's thresholds. The percentages of improvement in the EQ-5D-3L were moderate: 44 (48)% in the hip and 42 (44)% for the knee replacement population.

Conclusions: Distinctive percentage differences in patients' perception of improvement were observed when the paired data-specific capacity of benefit score was applied to examine responsiveness. This is useful in clinical practice as rationale for access to surgery at the individual-patient level. This study shows the importance of analytic methods and instruments for investigation of the health status in hip and/or knee replacement surgery. The study finding also supports the idea of using a generic measure along with the disease-specific instruments in terms of cross-validation.

Keywords: EQ-5D-3L Index; Hip and knee replacement; Internal responsiveness; OHS; OKS; Patient-reported outcome.

Fig. 1

The OHS and EQ-5D-3L – total population (1, 3) and the transition level (2, 4). Fitted 3rd degree Box-Cox regression lines 1 for the OHS total population and 2 by the patients’ self-assessed transition level. The 2nd degree Box-Cox regression estimates 3 for the EQ-5D-3L total hip surgery population and 4 by the patients’ self-assessed transition level. All the graphs are presented by age group additionally. Colourful dots indicate 50th percentile for each category, and grey dots indicate actual observations. Grey horizontal lines indicate each defined score improvement (e.g. 22 for the OHS and 0.428 for the hip EQ-5D-3L). Percentiles of the EQ-5D-3L show all over disperse patterns by the transition level whereas percentiles of the OHS show disperse patterns in ‘A little worse’ and ‘Much worse’ transition level. Model performance of the OKS and the knee EQ-5D-3L is provided in Supplementary Figure 1