caa a22 4500 606179100 CHVBK 20210128100759.0 cr unu---uuuuu 210128e20150301xx s 000 0 eng 10.1007/s11136-014-0808-3 doi (NATIONALLICENCE)springer-10.1007/s11136-014-0808-3 Improved statistical analysis of pre- and post-treatment patient-reported outcome measures (PROMs): the applicability of piecewise linear regression splines [Elektronische Daten] [M. Greene, O. Rolfson, G. Garellick, M. Gordon, S. Nemes] Purpose: Patient-reported health-related quality-of-life (HRQoL) measures such as the EuroQol 5 dimension (EQ-5D) index are commonplace when assessing healthcare providers or efficiency of medical techniques. HRQoL measures are generally bounded, and the magnitude of possible improvement depends on the pre-treatment HRQoL value. This paper aimed to assess and illustrated the possibility of modelling the relationship between pre- and post-treatment HRQoL measures with piecewise linear splines. Methods: The method was illustrated using a longitudinal dataset of 36,625 patients with one EQ-5D index before and one a year after total hip arthroplasty. We considered four models: intercept only model, single line regression, and segmented regression with 1 and 2 change points. The post-operative EQ-5D index served as the outcome, while the preoperative EQ-5D index was the predictor. Results: We found that a two-line regression best described the data with the lines meeting at 0.159 on the preoperative EQ-5D index scale. In the low preoperative group (with an initial preoperative index from −0.594 to 0.159), the predicted post-operative scores ranged from 0.368 to 0.765, with post-operative scores increasing 0.528 points for each unit in the preoperative score. In the high preoperative group (initial range from 0.159 to 1), the predicted post-operative scores ranged from 0.765 to 0.855, increasing 0.106 points for each unit in the preoperative score. Conclusions: Piecewise linear regression is a straightforward approach to analyse baseline and follow-up HRQoL measures such as the EQ-5D index. It can provide a reasonable approximation of the shape of the underlying relationship where the threshold and slopes prove informative and meaningful. Springer International Publishing Switzerland, 2014 EQ-5D nationallicence Segmented regression nationallicence Change point nationallicence Total hip arthroplasty nationallicence Greene M. Swedish Hip Arthroplasty Register, Centre of Registers Västra Götaland, Medicinargatan 18G, 413 45, Gothenburg, Sweden aut Rolfson O. Swedish Hip Arthroplasty Register, Centre of Registers Västra Götaland, Medicinargatan 18G, 413 45, Gothenburg, Sweden aut Garellick G. Swedish Hip Arthroplasty Register, Centre of Registers Västra Götaland, Medicinargatan 18G, 413 45, Gothenburg, Sweden aut Gordon M. Swedish Hip Arthroplasty Register, Centre of Registers Västra Götaland, Medicinargatan 18G, 413 45, Gothenburg, Sweden aut Nemes S. Swedish Hip Arthroplasty Register, Centre of Registers Västra Götaland, Medicinargatan 18G, 413 45, Gothenburg, Sweden aut Quality of Life Research Springer International Publishing 24/3(2015-03-01), 567-573 0962-9343 24:3<567 2015 24 11136 https://doi.org/10.1007/s11136-014-0808-3 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s11136-014-0808-3 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Greene M. Swedish Hip Arthroplasty Register, Centre of Registers Västra Götaland, Medicinargatan 18G, 413 45, Gothenburg, Sweden aut NATIONALLICENCE 700 1- Rolfson O. Swedish Hip Arthroplasty Register, Centre of Registers Västra Götaland, Medicinargatan 18G, 413 45, Gothenburg, Sweden aut NATIONALLICENCE 700 1- Garellick G. Swedish Hip Arthroplasty Register, Centre of Registers Västra Götaland, Medicinargatan 18G, 413 45, Gothenburg, Sweden aut NATIONALLICENCE 700 1- Gordon M. Swedish Hip Arthroplasty Register, Centre of Registers Västra Götaland, Medicinargatan 18G, 413 45, Gothenburg, Sweden aut NATIONALLICENCE 700 1- Nemes S. Swedish Hip Arthroplasty Register, Centre of Registers Västra Götaland, Medicinargatan 18G, 413 45, Gothenburg, Sweden aut NATIONALLICENCE 773 0- Quality of Life Research Springer International Publishing 24/3(2015-03-01), 567-573 0962-9343 24:3<567 2015 24 11136