Table 3.
Candidate predictors
| Socio-demographic characteristics | ||||
| Candidate predictor | Units/categories | Definition | Variable type (number of categories) | Source data |
| Age | Years | Year of birth subtracted from the year of study entry | Continuous | Primary care |
| Sex | Male/female | As recorded | Categorical (2) | Primary care |
| Ethnicity | White/mixed/Asian/Black/others | As recorded (codes collapsed into the five Census categories [18]) | Categorical (5) | Primary care, secondary care |
| Social deprivation | Index quintile | Patient Level Index of Multiple Deprivation, based on patient postcode | Categorical (5; data not accessible as continuous) | Secondary care |
| Lifestyle | ||||
| Candidate predictor | Units | Definition | Variable type | Source data |
| BMI | Index (kg/m2) | As recorded | Continuous | Primary care |
| Alcohol consumption | Non-drinker/ex-drinker/occasional drinker/moderate drinker/heavy drinker | Based on the records of daily and weekly units and drinker status codes [31] with equal classification for both sexes | Categorical (5) | Primary care |
| Smoking | Non-smoker/ex-smoker/current smoker | As recorded | Categorical (3) | Primary care |
| Use of injected drugs | Present/absent | As recorded | Categorical (2) | Primary care |
| Co-morbidities | ||||
| Candidate predictor | Units | Definition | Variable type | Source data |
| Hypertension | Present/absent | Diagnosis of hypertension or record of at least three high blood pressure readings within 1 year or at least two systolic or diastolic high blood pressure readings or prescriptions for blood pressure lowering medication within 6 months | Categorical (2) | Primary care, secondary care |
| Diabetes |
Type 1/type 2/ uncertain type/no diabetes |
Diagnosis of diabetes and type | Categorical (4) | Primary care, secondary care |
| Inflammatory bowel disease | Present/absent | Diagnosis of Crohn’s disease or ulcerative colitis | Categorical (2) | Primary care, secondary care |
| Mental illness and behavioural disorders | Present/absent | Diagnosis of schizophrenia, psychosis, bipolar disorder, another mood affective disorder, depression, anxiety or phobia, reaction to stress or adjustment disorder | Categorical (2) | Primary care, secondary care |
| Psoriasis | Present/absent | Primary and secondary care diagnoses, or diagnosis in one data source only and supportive information through referral, dermatologist visit, medication or positive laboratory test | Categorical (2) | Primary care, secondary care |
| Cardiovascular disease | Present/absent | Diagnosis of stable or unstable angina, myocardial infarction, cerebrovascular disease, peripheral arterial disease, another atherosclerotic disease, heart failure, bradycardia, tachycardia, cardiac valve disorder, endocarditis, venous thromboembolism, atrial fibrillation or cardiomyopathy | Categorical (2) | Primary care, secondary care |
| Cancer | Present/absent | As recorded | Categorical (2) | Primary care, secondary care |
| HIV | Positive/negative | As recorded | Categorical (2) | Primary care, secondary care |
| Co-morbidity score | Score | Charlson co-morbidity index excluding liver disease | Continuous | Primary care, secondary care |
| Laboratory tests | ||||
| Candidate predictor | Units | Definition | Variable type | Source data |
| Albumin | g/L | As recorded | Continuous | Primary care |
| ALP | units/L | As recorded | Continuous | Primary care |
| ALT | units/L | As recorded | Continuous | Primary care |
| AST | units/L | As recorded | Continuous | Primary care |
| Bilirubin | μmol/L | As recorded | Continuous | Primary care |
| GGT | units/L | As recorded | Continuous | Primary care |
| High-density lipoprotein | mmol/L | As recorded | Continuous | Primary care |
| Low-density lipoprotein | mmol/L | As recorded | Continuous | Primary care |
| Triglycerides | mmol/L | As recorded | Continuous | Primary care |
| Total cholesterol | mmol/L | As recorded | Continuous | Primary care |
| Platelet count | count/L | As recorded | Continuous | Primary care |
| Medications, procedures and immunisations | ||||
| Candidate predictor | Units | Definition | Variable type | Source data |
| Bariatric surgery | Yes/no | As recorded | Categorical (2) | Primary care, secondary care |
| Paracetamol overdose | Yes/no | As recorded | Categorical (2) | Primary care, secondary care |
| Statins | Yes/no | Prescription of statins or statins with ezetimibe | Categorical (2) | Primary care |
| Prescription non-steroid anti-inflammatory drugs | Yes/no | Prescription | Categorical (2) | Primary care |
| Opioid substitution treatment | Yes/no | Prescription for methadone or buprenorphine | Categorical (2) | Primary care |
| Cardiovascular drugs | Yes/no | Prescription for antiplatelet, antiarrhythmic, fibrinolytic, positive inotropic, hypertension and heart failure-related or lipid-regulating (excluding statins) drugs or beta blockers, diuretics, nitrates or warfarin | Categorical (2) | Primary care |
| Antibiotics | Yes/no | As recorded | Categorical (2) | Primary care |
| HAV vaccination | Received/not received | As recorded | Categorical (2) | Primary care |
| HBV vaccination | Received/not received | As recorded | Categorical (2) | Primary care |
| Pneumococcal vaccination | Received/not received | As recorded | Categorical (2) | Primary care |
| Influenza vaccination | Received/not received | As recorded | Categorical (2) | Primary care |