QResearch - qriskgeneralinformation

Technical Information about QRISK1 and QRISK2

This section is for those interested in understanding more of the technical details about QRISK2 rather than the general public.
There is a search definition which describe the data items which are needed to calculate the QRISK2 score (note this uses UK clinical coding schemes - an international version of QRISK2 is in development).
There is a detailed description and discussion of the multiple imputation methods used in QRISK1 (similar methods were used in QRISK2)
Here is a pdf of the QRISK2 paper as published in the British Medical Journal in June 2008
For a powerpoint presentation about advances in cardiovascular risk assessment by Dr Peter Brindle which was the plenary presentation at the recent HEART-UK conference (June 2008).

Glossary of terms

QRISK1: This was the original CVD risk prediction algorithm publihsed in the BMJ in 2007. As well as traditional risk factors such as age, sex, systolic blood pressure, cholesterol/HDL ratio, it also included deprivation, family history of premature CHD, body mass index and use of antihypertensive medication.
QRISK2: This is version two of the QRISK CVD risk predition algorithm. QRISK2 was published the BMJ in 2008. In addition to the variables included in QRISK1, QRISK2 also included self assigned ethnicity, rheumatoid arthritis, chronic renal disease, diabetes and atrial fibrillation, This is the first clinical release version which will be used in the UK.
QResearch: QResearch is the name of the database which contains electronic health records from primary care and which has been used to derive the algorithm
Risk prediction algorithm: This is a mathematical formula which uses risk factors to generate a percentage risk of developing a particular outcome (eg Cardiovascular Disease)
Outcome: The outcome refers to risk of cardiovascular disease.
Cardiovascular disease (CVD): This refers to coronary heart disease, stroke or transient ischaemic attack
Survivor function. The survivor function is a constant term which is the percentage of patients who haven’t had the outcome at X years. The term has been adjusted for other variables in the regression analysis.
Years over which risk is predicted: Patients may wish to know their risk over 1, 2, 5 etc years so a QRISK2 can be calculated for different time periods or for different ages.
Risk Factors: Risk factors are variables which are used to predict an individual’s risk of developing CVD. Broadly speaking, they can be divided into ‘modifiable’ risk factors (which the patient can change, such as body mass index) and ‘not modifiable’ (eg age).
Missing data: Missing data refers to when a particular variable (eg body mass index, systolic blood pressure, serum cholesterol/HDL ratio) is not recorded in the patient’s electronic record.
Multiple Imputation: This is a powerful statistical technique which takes accounts of missing data in the datasets used for the modelling and tends to result in more powerful and less biased results.
Complete data. Complete data refers to the situation when all the necessary variables to generate the score are recorded in the patient’s electronic record.
High risk: For the purposes of the guidelines, high risk is a CVD risk of >=20% over ten years.
Calculated risk: The calculated risk is the patient’s CVD risk score based on data which is already recorded in their electronic health records.
Estimated risk: The mean estimated risk is the patient’s CVD risk score which has been calculated on the bases of recorded data but where missing data for either BMI, systolic blood pressure or cholesterol/HDL ratio have been replaced using predicted mean values based on the patients age, sex, family history and smoking status. Zero will be substituted if townsend scores are missing.

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