Background: The World Health Organization/International Society of Hypertension (WHO/ISH) Hypertension Guidelines from 1999 propose a risk stratification scheme for estimating absolute risk for cardiovascular disease (CVD). Risk equations estimated by statistical methods are another way of predicting cardiovascular risk.
Objective: We studied the differences between these two approaches when applied to the same set of individuals with high blood pressure.
Design and methods: The two northernmost counties in Sweden (NSW) constitute one of the centres in the WHO MONICA (monitoring trends and determinants in cardiovascular disease) Project. Three population surveys have been carried out in 1986, 1990 and 1994, and were used to estimate a risk equation for predicting the 10-year risk of fatal/non-fatal stroke and myocardial infarction. Another MONICA sample from 1999, a total of 5997 subjects, was classified according to the recent WHO/ISH risk stratification scheme. A risk assessment was also performed, by using the risk equations from the NSW MONICA sample and Framingham risk equations.
Results: The agreement between the two methods was good when the values obtained from the risk equation were averaged for each risk group obtained from the risk classification by guidelines. However, if the predicted risk for each individual was considered, the agreement was poor for the medium and high-risk groups. Although the average risk for all individuals is the same, many subjects have a higher risk or a lower risk than predicted by guidelines.
Conclusions: Risk classification by the 1999 WHO/ISH Hypertension Guidelines is not accurate and detailed enough for medium- and high-risk patients, which could be of clinical importance in the medium risk group.