Effect of competing mortality risks on predictive performance of the QRISK3 cardiovascular risk prediction tool in older people and those with comorbidity: external validation population cohort study.

Background Primary prevention of cardiovascular disease (CVD) is guided by risk-prediction tools, but these rarely account for the risk of dying from other conditions (ie, competing mortality risk). In England and Wales, the recommended risk-prediction tool is QRISK2, and a new version (QRISK3) has been derived and internally validated. We aimed to externally validate QRISK3 and to assess the effects of competing mortality risk on its predictive performance. Methods For this retrospective population cohort study, we used data from the Clinical Practice Research Datalink. We included patients aged 25-84 years with no previous history of CVD or statin treatment who were permanently registered with a primary care practice, had up-to-standard data for at least 1 year, and had linkage to Hospital Episode Statistics discharge and Office of National Statistics mortality data. We compared the QRISK3-predicted 10-year CVD risk with the observed 10-year risk in the whole population and in important subgroups of age and multimorbidity. QRISK3 discrimination and calibration were examined with and without accounting for competing risks. Findings Our study population included 1 484 597 women with 42 451 incident CVD events (4·9 cases per 1000 person-years of follow-up, 95% CI 4·89-4·99), and 1 420 176 men with 53 066 incident CVD events (6·7 cases per 1000 person-years, 6·66-6·78), with median follow-up of 5·0 years (IQR 1·9-9·2). Non-CVD death rose markedly with age (0·4% of women and 0·5% of men aged 25-44 years had a non-CVD death vs 20·1% of women and 19·6% of men aged 75-84 years). QRISK3 discrimination in the whole population was excellent (Harrell's C-statistic 0·865 in women and 0·834 in men) but was poor in older age groups (<0·65 in all subgroups aged 65 years or older). Ignoring competing risks, QRISK3 calibration in the whole population and in younger people was excellent, but there was significant over-prediction in older people. Accounting for competing risks, QRISK3 systematically over-predicted CVD risk, particularly in older people and in those with high multimorbidity. Interpretation QRISK3 performed well at the whole population level when ignoring competing mortality risk. The tool performed considerably less well in important subgroups, including older people and people with multimorbidity, and less well again after accounting for competing mortality risk. Funding National Institute for Health Research.