Aim To assess the performance of the QRISK score for predicting cardiovascular disease in an independent external UK sample from general practice
Design Prospective open cohort study using routinely collected data from general practice.
Setting UK practices contributing to the THIN database and the QRESEARCH database.
Cohort The THIN validation cohort consisted of 1.07 million patients, aged 35-74 years registered at 280 THIN practices between 01 Jan 1995 and 01 April 2006 not on statins and free from diabetes and existing cardiovascular disease at baseline. The QRESEARCH validation cohort consisted of 0.61 million patients from 160 practices (one third of the full database) with data until 01 January 2007.
Endpoint First recorded diagnosis of cardiovascular disease i.e. incident diagnosis of cardiovascular disease between 01 Jan 1995 and either 01 April 2006 (THIN) or 01 April 2007 (QRESEARCH). Cardiovascular disease includes myocardial infarction, coronary heart disease, stroke and transient ischaemic attacks.
Risk factors Age, sex, smoking status, systolic blood pressure, ratio of total serum cholesterol/HDL cholesterol, body mass index, family history of coronary heart disease in first degree relative under 60 years, area measure of deprivation, existing treatment with antihypertensive agents.
Results Overall, the baseline characteristics of the THIN and QRESEARCH cohorts were similar though patients from THIN tended to be from more affluent areas and had lower recording of family history of coronary heart disease. QRISK performed better than Framingham for all of the discrimination and calibration statistics in both the THIN and the QRESEARCH cohorts. Framingham over-predicted risk by 28% in the THIN cohort while QRISK under-predicted risk by 10%. The validation statistics for both scores were similar in the THIN cohort and the QRESEARCH validation cohort. Conclusion This is the first external assessment of the QRISK cardiovascular risk prediction algorithm in an independent general practice population. The results indicated that QRISK is likely to provide more appropriate risk estimates than Framingham to help identify high risk patients based on age, sex and social deprivation in UK general practice. The results are also important since this is the first major head on comparison of two recently established major UK general practice databases, suggesting that the results of similar studies based on either database would be generalisable to the UK.
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