The UK National Collaborating Centre for Primary Care and Royal College of General Practitioners and NICE recommended in 2007 that statins should be used as part of the management strategy for the primary prevention of cardiovascular disease (CVD) for adults who have a 20% or greater 10-year risk of developing CVDin 2007. The NHS is introducing a population-wide vascular risk assessment programme, consisting of a systematic approach to assessing risk of vascular diseases for people aged 40 and 74 years of age not yet diagnosed with CVD or treated for risk factors. Several risk scores (including Framingham, ASSIGN and QRISK2) can be used to estimate 10-year CVD risk. A recent review showed inconsistent results of the prognostic ability of the most popular risk scores. In addition, the performance of the risk scores in predicting high CVD risk (≥20% over 10 years) remains uncertain, and the Framingham risk score now overestimates CVD risk for the UK population.
This study evaluated the performance of the current strategy to target statin treatment based on CVD risk scores using data from the UK Clinical Practice Research Datalink (CPRD) formerly known as the General Practice Research Database. Researchers identified two study populations: the first population included patients aged 35–74 years registered in CPRD practices (general population). The index date was between 1993 and 2011. Patients with a history prior to the index date of CVD or diabetes mellitus were excluded. The second population consisted of patients initiating statin treatment in 1993 or later (defined as patients with a first-ever statin prescription at least 1 year after start of CPRD data collection). Patients with a history of CVD prior to, or in the first 6 weeks after starting statin treatment, or with a history of diabetes mellitus were excluded in order to restrict the study population to primary prevention. The index date was the date of first-ever statin prescription (total of 3.8 million general population patients and 300,914 statin users aged 35–74 years. The 10-year CVD risks were predicted using the three published risk scores of Framingham, ASSIGN and QRISK2.
The following findings were reported:
• Statin prescribing increased substantially over time to patients with high 10-year CVD risk (≥20%): 7.0% of these received a statin prior to 2007, and 30.4% in 2007 onwards.
• Prescribing to patients with low risk (<15%) also increased (from 1.9% to 5.0%).
• Only about half the patients initiating statin treatment were high risk according to CVD risk score.
• The 5-year CVD risks, as observed during statin treatment, reduced over calendar time (from 17.0% to 7.1%).
• There was a large variation between general practices in the percentage of high-risk patients prescribed a statin in 2007 onwards, ranging from 8.2% to 61.5%. For low-risk patients, these varied from 2.1% to 29.1%.
The researchers extrapolated these numbers to the UK population and estimated that:
• About 600,000 patients may have been prescribed a statin since 2007 despite having a CVD risk below 15% with any of the risk scores.
• Over 2.8 million patients received statin while having a predicted 10-year CVD risk of over 15%.
• About 850 000 did not receive a statin despite having a 10-year CVD risk of over 15%.
The researchers note that the targeting of statins to high-risk patients has become less efficient in recent years, as both the CVD risks as predicted at baseline by the risk scores and the actual risks during statin treatment have reduced over time. They suggest from these results that GPs have indeed been undertaking more CVD risk assessments (as reflected by the increases in statin prescribing and recording of risk factors) but that the approaches in how high CVD risk is assessed vary between practices. They call for randomised trials for the best strategy to target statin treatment and manage CVD risk for primary prevention.