Health economics

This section presents the results of the health economic analyses comparing plaster cast with functional brace. We compare (1) missing data by treatment group; (2) resource use and economic costs for different health and social care categories; (3) distribution of the responses to the EQ-5D-5L questionnaires and the EQ-5D-5L utility scores; and (4) cost-effectiveness results of the base-case and sensitivity analyses.

Results of economic analysis

Table 20 shows the degree of missing health economic data by treatment group and follow-up time point. The missing data pattern is non-monotonic, as individuals with missing data at one follow-up time point could return to the trial subsequently. For example, there are more missing EQ-5D data at 6 months than at 9 months post injury. A similar pattern can be observed for economic costs. It is worth noting that the smaller number of participants with complete data for the entire duration of follow-up (baseline to 9 months post injury) was because of a strict application of the term missing (i.e. we considered a participant as having incomplete data if, for example, they responded positively to vising a GP surgery at 3 months but did not specify the number of consultations, despite all other resource use items being completed). However, for the cost-effectiveness analysis, imputation was not at the aggregate level, such that most of the data used for the analysis were based on actual participant responses.

Health and social care resource use

Table 25 (see Appendix 1) shows the resource use values for participants by treatment group, resource use category and follow-up period for complete cases. The values are presented for subcategories of resource use, including hospital inpatient and outpatient care, community health and social care, prescribed medications, equipment and aids, and productivity losses.

In terms of specific resource use at the 8-week follow-up (see Appendix 1, Table 25), notable differences were observed between the groups for the proportion prescribed anticoagulant as VTE prophylaxis treatment (0.72 vs. 0.59; p = 0.003), the mean number of NHS outpatient orthopaedic visits (2.63 vs. 1.80; p < 0.001), the mean number of NHS outpatient physiotherapy visits (0.23 vs. 0.46; p = 0.003), the mean number of GP surgery visits (0.10 vs. 0.19; p = 0.028) and the mean number of grab rail installations (0.05 vs. 0; p = 0.019). For all other resource use items, there were no noticeable differences between the groups.

Between 8 weeks and 3 months post injury (see Appendix 1, Table 25), there were differences in resource use between the groups for the proportion of participants prescribed analgesics (0.11 vs. 0.05; p = 0.015) and the proportion of participants prescribed other medications (0.02 vs. 0; p = 0.038). For all other resource use items, there were no noticeable differences between the groups.

There were no significant differences in resource use between the plaster cast and the functional brace groups at 6 or 9 months post injury.

Economic costs

Table 21 summarises the total NHS and PSS costs associated with resource use during the trial period among complete cases by cost category and by follow-up period. The mean direct intervention cost was £35.71 for the plaster cast group compared with £108.64 for the functional brace group; the mean difference of £72.93 was statistically significant at the 5% level. The mean total NHS and PSS costs were significantly lower in the functional brace group between randomisation and 8 weeks post injury and between 8 weeks and 3 months post injury, with mean between-group cost differences of £107.73 and £92.95, respectively. The mean total NHS and PSS cost during the entire follow-up period was £1182.64 for the plaster cast group and £1018.26 for the functional brace group; the mean between-group cost difference of £164.39 was not statistically significant at the 5% level. Figure 14 (see Appendix 1) shows the distribution of total NHS and PSS costs during the entire follow-up period and indicates that differences in measures of central tendency (i.e. mean, median) for total economic costs between the treatment groups were not driven by high costs generated by a small number of participants in the trial.

Health outcomes

Summary results of the EQ-5D-5L analysis are presented in detail Chapter 3, Analyses to address secondary outcomes and Ancillary analyses. Below we provide the cost-effectiveness results.

Cost-effectiveness results

The cost-effectiveness results are presented in Table 22, with plaster cast as the referent and functional brace as the comparator (i.e. functional brace minus plaster cast) for the estimation of ICER values. The analytic time horizon is the entire 9-month post-injury follow-up period of the trial. The joint distribution of costs and outcomes for the base-case analysis and sensitivity analyses is represented in Figures 6–13.

FIGURE 6 Cost-effectiveness scatterplot at 9 months for base-case analysis (NHS and PSS perspective, imputed, additionally controlled for pre-injury utility, ITT analysis). Reproduced from Costa et al.49 © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/licenses/by/4.0/. (Figure not reproduced here; see the original article.)

FIGURE 7 Cost-effectiveness acceptability curve at 9 months for base-case analysis (NHS and PSS perspective, imputed, additionally controlled for pre-injury utility, ITT analysis). Reproduced from Costa et al.49 © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/licenses/by/4.0/. (Figure not reproduced here; see the original article.)

FIGURE 8 Cost-effectiveness scatterplot at 9 months for complete cases (NHS and PSS perspective, ITT analysis). (Figure not reproduced here; see the original article.)

FIGURE 9 Cost-effectiveness acceptability curve for complete cases (NHS and PSS perspective, ITT analysis). (Figure not reproduced here; see the original article.)

FIGURE 10 Cost-effectiveness scatterplot for societal perspective (imputed, ITT analysis). (Figure not reproduced here; see the original article.)

FIGURE 11 Cost-effectiveness acceptability curve for societal perspective (imputed, ITT analysis). (Figure not reproduced here; see the original article.)

FIGURE 12 Cost-effectiveness scatterplot for CACE population (imputed, NHS and PSS perspective). (Figure not reproduced here; see the original article.)

FIGURE 13 Cost-effectiveness acceptability curve for CACE population (imputed, NHS and PSS perspective, covariate adjusted). (Figure not reproduced here; see the original article.)

Base-case analysis

Patients in the functional brace group experienced a non-statistically significant increase in QALYs in the base case (0.015 QALYs, 95% CI –0.0013 to 0.030 QALYs) over the 9-month follow-up period. In addition, mean NHS and PSS costs were lower in the functional brace group (mean cost difference –£103, 95% CI –£289 to £84). The ICER for the base-case analysis indicates that functional brace is the dominant procedure, as average costs for this intervention were lower and average benefits were greater than those for plaster cast.

Assuming cost-effectiveness thresholds of £15,000 per QALY, £20,000 per QALY and £30,000 per QALY, respectively, the probability that functional brace was cost-effective ranged from 0.96 to 0.97, and the NMB associated with functional brace was positive (see Table 22).

Sensitivity analyses

Comparing mean costs and QALY estimates using different analytical scenarios (complete case, societal perspective and CACE population) revealed that the cost-effectiveness results generally supported the base-case finding, with the exception of the sensitivity analysis that adopted a societal perspective. From the societal perspective, mean costs were higher in the functional brace group (£248, 94% CI –£476 to £972). However, the QALY results followed the same pattern as that for the base-case analysis and indicated that participants in the functional brace group experienced a non-statistically significant increase in QALYs over the 9-month follow-up period (0.015 QALYs, 95% CI –0.0042 to 0.031 QALYs). The probability that functional brace was cost-effective declined to a range of 0.50–0.69 at cost-effectiveness thresholds of £15,000 per QALY, £20,000 per QALY and £30,000 per QALY. The results of the mixed-effects model followed a similar pattern to those of the base-case (imputed) model: patients in the functional brace group experienced a non-statistically significant increase in QALYs (0.014 QALYs, 95% CI –0.0018 to 0.031 QALYs) over the 9-month follow-up period. In addition, mean NHS and PSS costs were lower in the functional brace group (mean cost difference –£135, 95% CI –£342 to £71).

The results of the sensitivity analyses to the MAR assumption, presented in Appendix 1, indicate that the cost-effectiveness of functional brace remained stable across all of the MAR departure scenarios. In addition, Figure 17 shows that a change in cost-effectiveness decision is likely to occur if participants with missing HRQoL data have up to 50% lower HRQoL than trial participants with similar characteristics whose HRQoL data are available.

Long-term economic modelling

The protocol allowed for decision-analytic modelling to estimate the longer-term cost-effectiveness of functional brace or plaster cast. However, we note that cost and health utility values started to converge from the 3-month follow-up time point and converged at subsequent time points, even though functional brace was cost-effective over the entire follow-up period. It was therefore concluded that longer-term extrapolation of cost-effectiveness of functional brace is highly unlikely to be meaningful. Furthermore, we did not identify external studies that compared differences in economic costs, functional outcomes or HRQoL beyond 9 months post injury between non-surgical patients treated with plaster cast and those treated with functional brace. This lack of the data needed to parameterise a model further challenged any efforts to conduct longer-term decision modelling.