Defining and validating chronic diseases
In addition, recently published research has highlighted increased cardiovascular risk and potential prognostic importance for erectile dysfunction,22 23 24 migraine,25 and blood pressure variability.26 We therefore derived and validated a new version of the algorithms, QRISK3, to determine whether these factors should be incorporated into the algorithms to improve estimation of cardiovascular risk for these patients.
Our outcome was cardiovascular disease, which was defined as a composite outcome of coronary heart disease, ischaemic stroke, or transient ischaemic attack.
In women, the algorithm explained 59.6% of the variation in time to diagnosis of cardiovascular disease (R, with higher values indicating more variation), and the D statistic was 2.48 and Harrell’s C statistic was 0.88 (both measures of discrimination, with higher values indicating better discrimination).
The corresponding values for men were 54.8%, 2.26, and 0.86.
The QResearch database is linked at individual patient level to hospital admissions data (Hospital Episode Statistics), and mortality records obtained from the Office for National Statistics.
The records are linked using a pseudonymised NHS number specific to the QResearch database.
The Read codes are listed in table 1 of the web appendix.