clinical calculators.
evidence-based scoring tools, validated questionnaires, and decision rules β each with interpretation guidance, clinical pearls, and references.
4Ts Score (Heparin-Induced Thrombocytopenia)
The 4Ts score estimates the pretest probability of heparin-induced thrombocytopenia (HIT) based on four clinical criteria: degree of Thrombocytopenia, Timing of platelet fall, presence of Thrombosis, and likelihood of oTher causes. It is the most widely used clinical tool for HIT pre-test probability assessment.
CHAβDSβ-VASc
CHAβDSβ-VASc estimates annual stroke risk in non-valvular atrial fibrillation to guide anticoagulation decisions. It scores: CHF (1), Hypertension (1), Age β₯75 (2), Diabetes (1), Stroke/TIA (2), Vascular disease (1), Age 65β74 (1), Sex female (1).
Caprini VTE Risk Score
The Caprini Risk Assessment Model stratifies surgical patients by VTE risk using a comprehensive set of risk factors weighted 1β5 points. It guides the intensity of perioperative thromboprophylaxis from early ambulation alone to pharmacologic prophylaxis with extended duration.
Padua VTE Prediction Score
The Padua Prediction Score stratifies acutely ill medical inpatients by VTE risk to guide thromboprophylaxis decisions. A score β₯4 identifies high-risk patients who should receive pharmacologic prophylaxis.
IMPROVE Bleeding Risk Score
The IMPROVE Bleeding Risk Score estimates the risk of major bleeding in acutely ill medical inpatients, helping clinicians decide whether the benefit of pharmacologic VTE prophylaxis outweighs the bleeding risk.
TIMI Risk Score (UA/NSTEMI)
The TIMI risk score for unstable angina/NSTEMI estimates the probability of death, MI, or severe recurrent ischaemia requiring urgent revascularisation within 14 days. It uses 7 binary variables available at the time of presentation.
Age-Adjusted D-dimer Cutoff
Calculates an age-adjusted D-dimer threshold (age Γ 10 Β΅g/L FEU) for patients β₯50 years to improve the specificity of D-dimer testing in older adults with suspected VTE, reducing unnecessary CTPA imaging while maintaining safety.
CURB-65
CURB-65 stratifies community-acquired pneumonia severity using five bedside criteria to guide place-of-care decisions. Each criterion scores 1 point: Confusion, Urea >7 mmol/L, Respiratory rate β₯30, Blood pressure (systolic <90 or diastolic β€60), and age β₯65.
Canadian C-Spine Rule
The Canadian C-Spine Rule is a three-step branching algorithm for determining whether cervical spine imaging is needed in alert, stable trauma patients. Step 1 identifies high-risk features mandating imaging. Step 2 identifies low-risk features permitting range-of-motion assessment. Step 3 tests active neck rotation.
Canadian CT Head Rule
The Canadian CT Head Rule determines which adults with minor head injury (GCS 13β15) require CT imaging. It identifies high-risk factors (100% sensitive for neurosurgical intervention) and medium-risk factors (sensitive for clinically important brain injury).
Glasgow Coma Scale (GCS)
The Glasgow Coma Scale quantifies level of consciousness across three components: eye opening, verbal response, and motor response. Total score ranges from 3 (deep coma) to 15 (fully alert). It is the most widely used consciousness assessment tool in acute and trauma care worldwide.
HEART Score
The HEART Score estimates short-term (6-week) risk of major adverse cardiac events (MACE) in patients presenting with chest pain. It uses five elements: History, ECG, Age, Risk factors, and Troponin.
NEWS2 (National Early Warning Score 2)
NEWS2 is the NHS standard early warning scoring system for detecting and responding to clinical deterioration in acutely ill patients. It scores 7 physiological parameters routinely measured in hospitals: respiratory rate, oxygen saturation, supplemental oxygen, temperature, systolic blood pressure, heart rate, and level of consciousness.
NEXUS C-Spine Criteria
The NEXUS (National Emergency X-Radiography Utilization Study) criteria identify blunt trauma patients at very low risk of cervical spine injury who do not require imaging. All 5 low-risk criteria must be met to clear the c-spine clinically.
PECARN Pediatric Head Injury Rule
PECARN identifies children with minor head trauma at very low risk of clinically important traumatic brain injury (ciTBI), enabling safe reduction of CT imaging and associated radiation exposure. Uses age-stratified algorithms for children <2 years and β₯2 years.
PERC Rule (Pulmonary Embolism Rule-out Criteria)
The PERC rule identifies very-low-risk patients in whom pulmonary embolism can be excluded without D-dimer testing or imaging. All 8 criteria must be negative for PE to be ruled out. The rule applies ONLY to patients with LOW clinical pretest probability.
SOFA Score (Sequential Organ Failure Assessment)
SOFA quantifies multi-organ dysfunction across 6 systems (respiration, coagulation, liver, cardiovascular, CNS, renal), each scored 0β4. Total score ranges 0β24. It is the cornerstone of the Sepsis-3 definition: sepsis = suspected infection + acute SOFA increase β₯2.
Wells Criteria for PE
The Wells criteria for PE estimate the pretest probability of pulmonary embolism to guide the diagnostic pathway β determining whether D-dimer, CTPA, or empiric treatment is the appropriate next step.
Wells Score for DVT
The Wells score for DVT stratifies patients into low, moderate, and high pretest probability groups to guide D-dimer and imaging decisions in suspected deep vein thrombosis.
YEARS Algorithm (PE Workup)
The YEARS algorithm simplifies PE diagnosis by combining three clinical items with a variable D-dimer threshold. If no YEARS items are positive, a higher D-dimer threshold (1000 Β΅g/L) is used for exclusion; if β₯1 item is positive, the standard threshold (500 Β΅g/L) applies. This reduces CTPA imaging by ~14% compared to conventional pathways.
qSOFA (Quick SOFA)
The qSOFA is a rapid bedside screening tool using three simple clinical criteria to identify adult patients with suspected infection who are at greater risk of poor outcomes. It requires no laboratory tests and can be performed in seconds.
APACHE II
APACHE II is the most widely used ICU severity-of-illness score. It combines the Acute Physiology Score (12 variables using worst values in first 24h), age points, and chronic health evaluation to predict hospital mortality and enable ICU benchmarking.
FOUR Score (Full Outline of UnResponsiveness)
The FOUR Score is a 16-point coma assessment scale designed to address the limitations of the GCS, particularly in intubated patients. It assesses four components each scored 0β4: Eye response, Motor response, Brainstem reflexes, and Respiration. Unlike GCS, it does not require a verbal response and directly assesses brainstem function and respiratory pattern.
ISTH DIC Score
The ISTH scoring system for overt disseminated intravascular coagulation uses platelet count, fibrin markers (D-dimer/FDPs), prothrombin time prolongation, and fibrinogen level. A score β₯5 is compatible with overt DIC.
Revised Geneva Score (PE)
The Revised Geneva Score is a fully standardised (no subjective items) pretest probability assessment for pulmonary embolism. Unlike Wells PE, all criteria are objective, eliminating inter-rater variability from the 'PE most likely diagnosis' assessment.
Simplified PESI (sPESI)
The simplified Pulmonary Embolism Severity Index stratifies patients with confirmed PE into low-risk (sPESI 0) and higher-risk (sPESI β₯1) groups, primarily to identify candidates for outpatient management.
Child-Pugh Score
The Child-Pugh score classifies the severity of chronic liver disease/cirrhosis using five clinical and laboratory variables. It stratifies patients into class A (well-compensated), B (significant compromise), or C (decompensated) with corresponding survival and operative risk estimates.
FIB-4 Index
FIB-4 is a simple non-invasive index for liver fibrosis risk stratification calculated from age, AST, ALT, and platelet count. Formula: (Age Γ AST) / (Platelets Γ βALT). It is widely used as a first-line triage tool for identifying patients who may have advanced hepatic fibrosis.
Glasgow-Blatchford Score (GBS)
The Glasgow-Blatchford Score identifies patients with acute upper GI bleeding who need clinical intervention (transfusion, endoscopy, surgery) versus those who can be safely managed as outpatients. A score of 0 identifies the lowest-risk group.
MELD Score
MELD estimates 3-month mortality risk in patients with end-stage liver disease using serum creatinine, bilirubin, and INR. It is the primary score used for organ allocation in liver transplantation (UNOS/Eurotransplant).
MELD-Na
MELD-Na incorporates serum sodium into the standard MELD score to improve mortality prediction in cirrhosis. Hyponatraemia is common in advanced cirrhosis (dilutional, from portal hypertension) and is an independent predictor of waitlist mortality that standard MELD does not capture.
AIMS65 Score
AIMS65 predicts in-hospital mortality in patients with acute upper GI bleeding using five simple criteria: Albumin <30, INR >1.5, altered Mental status, Systolic BP β€90, and age β₯65.
Lille Score (Alcoholic Hepatitis)
The Lille score assesses the response to corticosteroid treatment in severe alcoholic hepatitis at day 7. A score >0.45 identifies non-responders in whom steroids should be discontinued to avoid unnecessary infection risk.
Maddrey Discriminant Function
The Maddrey Discriminant Function assesses severity of alcoholic hepatitis using prothrombin time prolongation and bilirubin. Formula: 4.6 Γ (patient PT β control PT) + bilirubin (mg/dL). A DF β₯32 defines severe disease and historically guides the decision to initiate corticosteroid therapy.
NAFLD Fibrosis Score (NFS)
The NAFLD Fibrosis Score is a non-invasive composite score predicting advanced liver fibrosis (F3βF4) in patients with NAFLD/MASLD. It uses age, BMI, diabetes status, AST/ALT ratio, platelets, and albumin.
Clinical Frailty Scale (CFS)
The Clinical Frailty Scale is a 9-point ordinal scale that grades frailty based on functional status 2 weeks before the current illness. It ranges from 1 (very fit) to 9 (terminally ill) and is widely used in acute care for prognostication, triage, and treatment escalation decisions.
Confusion Assessment Method (CAM)
The Confusion Assessment Method is a validated algorithm for identifying delirium at the bedside. It requires the presence of (1) acute onset and fluctuating course AND (2) inattention, PLUS either (3) disorganised thinking OR (4) altered level of consciousness. CAM-positive = delirium likely.
Mini-Cog
The Mini-Cog is a brief cognitive screening tool combining 3-word recall and clock drawing. It takes 2β4 minutes and screens for cognitive impairment suggestive of dementia. Scoring: 0 recall = positive (impaired); 3 recall = negative (normal); 1β2 recall β clock drawing determines result.
Geriatric Depression Scale (GDS-15)
The Geriatric Depression Scale (15-item short form) is a yes/no questionnaire designed specifically for depression screening in older adults. It avoids somatic symptoms (fatigue, sleep, appetite) that overlap with physical illness in the elderly, making it more specific than the PHQ-9 in this population.
Katz ADL Index
The Katz Index of Independence in Activities of Daily Living assesses functional status across 6 basic ADLs: bathing, dressing, toileting, transferring, continence, and feeding. Score ranges from 0 (fully dependent) to 6 (fully independent).
Morse Fall Scale
The Morse Fall Scale identifies hospitalised patients at risk of falling using six assessment items. It is one of the most widely used inpatient fall risk screening tools, guiding fall prevention interventions.
Anion Gap
The anion gap measures the difference between measured cations (NaβΊ) and measured anions (Clβ» + HCOββ») in serum. It identifies unmeasured anions and is essential for characterising metabolic acidosis as either high anion gap (HAGMA) or normal anion gap (NAGMA).
CKD-EPI 2021 eGFR (Creatinine)
The CKD-EPI 2021 equation estimates glomerular filtration rate from serum creatinine, age, and sex using the race-free 2021 formula. It is the current recommended equation for eGFR calculation in adults worldwide, replacing the 2009 equation that included a race coefficient.
Cockcroft-Gault Creatinine Clearance
The Cockcroft-Gault equation estimates creatinine clearance from age, weight, sex, and serum creatinine. It is the standard formula referenced by most drug labels for renal dose adjustments, and gives an estimate in mL/min (not normalised to BSA).
KDIGO AKI Staging
KDIGO AKI staging classifies acute kidney injury severity into Stages 1β3 based on serum creatinine changes from baseline and/or urine output criteria. The higher of the two criteria determines the stage.
Fractional Excretion of Sodium (FENa)
FENa calculates the percentage of filtered sodium excreted in urine, helping differentiate prerenal AKI (sodium avidly retained, FENa <1%) from intrinsic renal injury (FENa >3%). Formula: (Urine Na Γ Serum Cr) / (Serum Na Γ Urine Cr) Γ 100.
Kidney Failure Risk Equation (KFRE)
The Kidney Failure Risk Equation estimates the 2- and 5-year probability of progression to kidney failure (requiring dialysis or transplant) in patients with CKD G3βG5. The 4-variable version uses age, sex, eGFR, and uACR.
NIH Stroke Scale (NIHSS)
The NIH Stroke Scale quantifies neurological deficit severity across 15 examination items covering consciousness, gaze, visual fields, facial movement, limb strength, ataxia, sensation, language, dysarthria, and neglect. Score ranges from 0 (no deficit) to 42 (maximum deficit). It is the standard stroke severity assessment worldwide.
ABCDΒ² Score (TIA Stroke Risk)
The ABCDΒ² score predicts short-term stroke risk after a transient ischaemic attack using five clinical features: Age, Blood pressure, Clinical presentation, Duration, and Diabetes.
Hunt & Hess Grade (SAH)
The Hunt & Hess grading system classifies the clinical severity of aneurysmal subarachnoid haemorrhage from Grade I (asymptomatic/mild headache) to Grade V (deep coma). It is the most widely used clinical SAH grading system and correlates with surgical risk and overall prognosis.
ICH Score
The ICH Score predicts 30-day mortality after intracerebral haemorrhage using five readily available clinical and radiographic features: GCS, ICH volume, presence of IVH, infratentorial origin, and age β₯80.
Modified Rankin Scale (mRS)
The modified Rankin Scale is the standard disability outcome measure in stroke medicine. It grades global disability from 0 (no symptoms) to 5 (severe disability/bedridden) and 6 (dead). It is the primary endpoint in most major stroke trials.
WFNS SAH Scale
The World Federation of Neurosurgical Societies scale grades aneurysmal SAH severity using GCS and presence of major focal neurological deficit. It provides a more standardised and reproducible grading system compared to Hunt & Hess.
ASA Physical Status Classification
The ASA Physical Status Classification system grades a patient's pre-operative physical condition from ASA I (healthy) to ASA VI (brain-dead organ donor). It is the most widely used pre-operative risk classification system globally and correlates with perioperative morbidity and mortality.
EuroSCORE II (Cardiac Surgery Risk)
EuroSCORE II predicts in-hospital mortality after cardiac surgery using 18 patient, cardiac, and operation-related variables in a logistic regression model. It replaced the additive and logistic EuroSCORE I and is the standard cardiac surgical risk tool in Europe.
Surgical Apgar Score
The Surgical Apgar Score uses three intraoperative variables β estimated blood loss, lowest heart rate, and lowest mean arterial pressure β to predict major complications and death within 30 days of surgery.
ASCVD Pooled Cohort Equations (2013 ACC/AHA)
The Pooled Cohort Equations estimate the 10-year risk of a first atherosclerotic cardiovascular event (MI or stroke) in adults aged 40β79 without prior ASCVD. Used to guide statin therapy and preventive intensity per ACC/AHA guidelines.
Body Mass Index (BMI)
Calculate body mass index from height and weight using the standard WHO formula (weight in kg divided by height in metres squared). BMI is the most widely used screening measure for weight classification in adults.
FRAX (Fracture Risk Assessment Tool)
FRAX estimates the 10-year probability of a major osteoporotic fracture (hip, spine, forearm, humerus) and hip fracture specifically, using clinical risk factors with or without femoral neck BMD. Country-specific models are available for >70 countries.
QRISK3 (10-year CVD Risk)
QRISK3 estimates the 10-year risk of cardiovascular disease (heart attack or stroke) for adults aged 25β84 in the UK. It is the NICE-recommended CVD risk tool and uses clinical, demographic, and deprivation data including conditions not captured by other risk scores (SLE, atypical antipsychotics, migraine, erectile dysfunction, severe mental illness).
SCORE2 (ESC 10-year CVD Risk)
SCORE2 estimates 10-year risk of fatal and non-fatal cardiovascular events for European adults aged 40β69 without prior CVD or diabetes. SCORE2-OP extends to ages 70β89. It replaces the original SCORE (fatal CVD only) with region-specific calibration across four European risk regions.
A1C to Estimated Average Glucose (eAG)
Converts HbA1c to estimated average glucose (eAG) using the ADAG regression equation. This helps patients understand their A1c result in the same units as their daily glucose readings.
ADA Diabetes Risk Test
The ADA Diabetes Risk Test is a brief questionnaire to identify individuals at increased risk of type 2 diabetes. A score β₯5 indicates higher risk and should prompt glucose/HbA1c testing. No blood tests required for the screening step.
Body Surface Area (Mosteller)
Calculates body surface area using the Mosteller simplified formula: BSA (mΒ²) = β(height (cm) Γ weight (kg) / 3600). BSA is primarily used for drug dosing (especially chemotherapy) and physiological normalisation.
Charlson Comorbidity Index (CCI)
The Charlson Comorbidity Index quantifies the burden of comorbid diseases to predict 10-year mortality risk. It assigns weighted scores (1β6) to 19 conditions based on their impact on mortality. The CCI is the most widely used comorbidity index in clinical research.
FINDRISC (Finnish Diabetes Risk Score)
FINDRISC is an 8-item non-laboratory questionnaire that predicts the 10-year risk of developing type 2 diabetes. It uses age, BMI, waist circumference, physical activity, diet, BP medication, history of high glucose, and family history. No blood tests are required.
PEG Pain Scale
The PEG is an ultra-brief 3-item pain assessment scale measuring Pain intensity, interference with Enjoyment of life, and interference with General activity. The score is the average of the three items (0β10). It is designed for longitudinal monitoring of chronic pain in primary care.
Oswestry Disability Index (ODI)
The Oswestry Disability Index is the most widely used condition-specific disability measure for low back pain. It assesses 10 functional domains (pain intensity, personal care, lifting, walking, sitting, standing, sleeping, social life, travelling, employment). Score = (sum of items / 50) Γ 100%.
AUDIT-C
The AUDIT-C is a 3-item alcohol consumption screening tool derived from the first 3 questions of the full AUDIT (WHO). It identifies hazardous drinking and alcohol use disorders with high sensitivity. Total score ranges from 0 to 12.
Columbia-Suicide Severity Rating Scale (C-SSRS)
The Columbia-Suicide Severity Rating Scale is a structured assessment of suicidal ideation severity and behaviour. It progresses from passive ideation (wishing to be dead) through active ideation with increasing specificity (method, intent, plan) to suicidal behaviour (attempts, preparation). It is the most widely used structured suicide risk assessment tool worldwide.
GAD-7 (Generalized Anxiety Disorder-7)
The GAD-7 is a 7-item self-report questionnaire that screens for generalised anxiety disorder and measures anxiety symptom severity. Each item is scored 0β3 over the past two weeks, with total scores ranging from 0 to 21. It is the most widely used brief anxiety screening tool in primary care.
PHQ-9 (Patient Health Questionnaire-9)
The PHQ-9 is a 9-item self-report questionnaire that scores each of the DSM criteria for major depressive disorder on a 0β3 severity scale. It is the most widely validated depression screening and severity monitoring tool in primary care worldwide. Total scores range from 0 to 27.
AUDIT (Alcohol Use Disorders Identification Test)
The full 10-item AUDIT (WHO) comprehensively screens for hazardous drinking, harmful drinking, and alcohol dependence. It covers consumption (Q1β3), dependence symptoms (Q4β6), and alcohol-related harms (Q7β10). Scores range 0β40.
DAST-10 (Drug Abuse Screening Test)
The DAST-10 is a 10-item yes/no screening questionnaire for drug-related problems (excluding alcohol and tobacco). It provides a quantitative index of the degree of consequences related to drug misuse over the past 12 months.
Mood Disorder Questionnaire (MDQ)
The Mood Disorder Questionnaire is a brief screening tool for bipolar spectrum disorders. It assesses 13 symptoms of mania/hypomania, whether they occurred together, and their impact. A positive screen requires β₯7 symptoms + clustering + moderate-serious impairment.
PHQ-15 (Somatic Symptom Severity)
The PHQ-15 measures somatic symptom severity across 15 common physical symptoms. Each item is scored 0β2 ('not bothered' to 'bothered a lot'), with total scores ranging from 0 to 30. Higher scores correlate with functional impairment, healthcare utilisation, and comorbid psychiatric conditions.
Asthma Control Test (ACT)
The Asthma Control Test is a 5-item patient-reported questionnaire assessing asthma control over the past 4 weeks. Scores range from 5 (poorest) to 25 (complete control). It guides step-up and step-down treatment decisions.
COPD Assessment Test (CAT)
The COPD Assessment Test is an 8-item patient-reported questionnaire measuring the impact of COPD on health status. Each item is scored 0β5, giving a total range of 0β40. It is used in the GOLD COPD assessment framework alongside exacerbation history to guide therapy.
STOP-Bang Questionnaire
The STOP-Bang questionnaire is an 8-item screening tool for obstructive sleep apnoea. Each item scores 1 point: Snoring, Tiredness, Observed apnoeas, blood Pressure, BMI >35, Age >50, Neck circumference >40 cm, and male Gender.
mMRC Dyspnoea Scale
The modified Medical Research Council dyspnoea scale grades functional breathlessness on a 0β4 scale. It is used alongside exacerbation history in the GOLD COPD assessment framework to guide treatment escalation.
BODE Index (COPD Prognosis)
The BODE index is a multidimensional COPD prognostic score incorporating Body mass index, airflow Obstruction (FEVβ), Dyspnoea (mMRC), and Exercise capacity (6MWD). It predicts mortality better than FEVβ alone.
Epworth Sleepiness Scale (ESS)
The Epworth Sleepiness Scale quantifies subjective daytime sleepiness across 8 common situations. Scores range from 0 to 24, with β₯10 generally considered abnormal. It is used to screen for excessive daytime sleepiness and monitor treatment response (e.g., CPAP in OSA).