Although this large European trial demonstrated that a nurse-coordinated preventive cardiology programme in primary care helped more high-risk patients to achieve the lifestyle and risk factor targets in comparison with UC, this does not appear to be cost-effective. However, these cost-effectiveness analyses require careful qualification because they are subject to a number of uncertainties which are a consequence of the study design and important limitations in the statistical model used.
The differences in the adjusted and unadjusted results emphasise that the study design, based on matching pairs of general practices in each country, did not eliminate baseline differences between the two groups in cardiovascular risk factors. These differences meant that the two groups had different levels of baseline risk, higher in intervention than UC, but the economic results have adjusted for these baseline differences. Though these differences were small in absolute terms they have a substantial effect on the estimates of absolute risk of future cardiovascular events, and therefore on the difference in effectiveness between intervention and UC. Additionally, the study recorded its primary endpoints at baseline and at 1 year, and to avoid ‘contamination’ by recording risk factor levels in UC, baseline measurements were only made in a subsample of UC patients. Thus, we do not have before and after measurements for 75% of the UC patients.
Our cost-effectiveness analysis did not include partners. If partners were included it might improve the cost-effectiveness, but we have no good measure of the effect on partners to know how substantial the impact on the incremental cost-effectiveness ratio might be.
Our estimates of the risk of future CVD events are based on published risk equations.5
These are derived from a large, well-characterised cohort (8491 participants) and predict CVD risk as opposed to CHD risk alone. The C statistic for the model ranges from 0.76 (men) to 0.79 (women), suggesting that additional risk factors could potentially improve the model's discriminatory power. Other risk models have included risk factors such as family history of CVD, social deprivation and biomarkers, for example, hs-CRP,16
although these models also have their own limitations.
However, to date lifestyle factors such as dietary habits and physical inactivity, although important in the aetiology of CHD18
and independent of the other major risk factors, have not been included in such risk scores, because they are difficult to accurately quantify. The omission of these important lifestyle factors in the Framingham risk equations may be particularly relevant in our study as the cornerstone of the EUROACTION programme was lifestyle change which was clearly evident in the study's most striking achievements in this area including significantly higher fruit and vegetable consumption (p=0.005); physical activity levels (p=0.01) and weight loss (p=0.005).
It is thus possible that our estimates of relative differences in absolute risk between the groups may understate the full effects of the intervention on long-term CVD risk. However, we showed that the risk equations are able to predict CHD events in the study population in the 1-year follow-up period, but the accuracy of the risk equations over the 10-year period of our study remains untested.
Our modelling also requires an assumption about how long any differential effect of the intervention persists. Nothing is known about the longer-term effects of EUROACTION, and there are few studies that have looked at longer-term changes. The longest follow-up to a relevant lifestyle change appears to be the OXCHECK study, which showed that the benefits of health checks were sustained over 3 years.19
However, whatever the duration of effect beyond the trial, and even when a 25-year model was used, the policy conclusions remain the same.
Finally, our model uses a regression analysis approach so that a UK-specific estimate can be drawn from the complete multinational EUROACTION dataset on net resource use, costs and net effects of the intervention. The epidemiological, utilities and cost data for the longer-term modelling of risk and events are based on UK data alone. Thus, the results are applicable to the UK and not specifically to the other EUROACTION countries. While formal analysis would be needed to confirm this, the coefficients on the country parameters in the regression analyses of both costs and outcomes suggest that the cost-effectiveness would be broadly similar in the other countries.