Regional adjustment

Adjustment factors for use of PROCAM scores outside Germany

Calculation of risk-factor scores requires good quality long-term prospective epidemiological data. In most of the world, such data are in short supply. In addition, even within a circumscribed geographical region such as continental Europe, significant variations of absolute risk may be seen among persons with similar risk profiles. For this reason, a score derived in one population may give an incorrect estimate of absolute risk when used in another.

The ideal solution to this dilemma would be to gather more prospective data in different regions of interest. This is very expensive and would take many years before results are available. In addition, the widespread and variable use of lipid-lowering and antihypertensive agents makes it very difficult to assess the natural history of CHD in future studies. A pragmatic approach to solving the problem of regional variability in coronary risk is to recalibrate existing algorithms based on cross-sectional observational data, which are much easier to collect.

Table 1 presents such an attempt to recalibrate the PROCAM score using the CHD morbidity, mortality and case fatality data collected as part of the World Health Organization Monitoring of Trends in Cardiovascular Disease (MONICA) project. Recalibration data are also available for the Framingham algorithm.
In the MONICA¹ study the citizens of Augsburg, a town in southern Germany, were found to have a coronary event rate and a risk factor profile similar to those of the participants in the PROCAM Study. The ratio of CHD mortality in a specific region relative to the CHD mortality observed in the Augsburg MONICA cohort may therefore be used as a rough conversion factor when calculating absolute coronary event rates using the PROCAM score in other populations. This approach assumes comparable case fatality rates in Augsburg and any comparison region. Current evidence suggests that the case fatality of CHD in many countries is about 40%. In other words, the incidence of coronary events (defined as nonfatal or fatal MI and sudden coronary death) is about 2.5 times the CHD mortality.

This conversion chart may therefore provide a rough estimate of absolute coronary risk when the PROCAM scores are used outside Germany.

1. Tunstall-Pedoe, H., Kuulasmaa, K., Mähönen, M. et al. Contribution of trends in survival and coronary-event rates to changes in coronary heart disease mortality: 10-year results from 37 WHO MONICA project populations. Monitoring trends and determinants in cardiovascular disease. Lancet 1999; 353: 1547-1557.

TABLE 1. Adjustment factors for use of PROCAM scores outside Germany.