1,329 calculators and references across 60 specialties, with formula confidence shown up front.
Serum Albumin Ascitic Albumin Serum Ascites Albumin Gradient SAAG Explanation and Clinical Context SAAG represents the difference between serum albumin concentration and ascitic albumin concentration. It is a validated method to classify the underlying mechanism of ascites formation and to guide diagnostic reasoning. A value of one point one g per dL or more indicates portal hypertension related etiologies because th
Signal-Averaged ECG (SAECG) Abnormality Index: Explanation and Clinical Context SAECG is a specialized electrocardiographic technique used to detect subtle abnormalities in ventricular depolarization that are not visible on standard ECG. The SAECG Abnormality Index quantifies risk for ventricular arrhythmias by scoring three primary parameters: filtered QRS duration, low amplitude signal duration, and root mean squar
SAFE-TAVR Score: Explanation and Clinical Context The SAFE-TAVR Score is a clinical tool designed to assess the risk of pericardial effusion or cardiac tamponade following Transcatheter Aortic Valve Replacement (TAVR). It incorporates patient-specific factors such as age, sex, presence of chronic kidney disease, hypertension, ventricular function, and access site to stratify risk. This score aids clinicians in identi
Spatial Angle Index (SAI QRST): Explanation and Clinical Context SAI QRST is a quantitative ECG-derived index that measures the spatial angle between the QRS complex and T wave vectors in three-dimensional space. It reflects the degree of heterogeneity in ventricular depolarization and repolarization. Higher values of SAI QRST indicate greater electrical instability and are associated with increased risk of ventricul
: Explanation and Clinical Context This estimator quantifies the potential impact of reducing average daily salt consumption on population-level blood pressure and cardiovascular risk. Excessive sodium intake is a major modifiable determinant of hypertension, which in turn is a leading cause of stroke, ischemic heart disease, and chronic kidney disease. Meta-analyses have consistently demonstrated that for every 1 gr
SAMe-TT₂R₂ Score: Explanation and Clinical Context The SAMe-TT₂R₂ score is a validated clinical tool to predict the quality of warfarin anticoagulation control in patients with atrial fibrillation. It integrates demographic and clinical factors including sex, age, comorbidities, concomitant interacting drugs, tobacco use, and race. A score of 0–2 predicts likely good anticoagulation control (time in therapeutic range
Simplified Acute Physiology Score II (SAPS II): Explanation and Clinical Context SAPS II is a validated intensive care unit (ICU) mortality prediction model designed to estimate the probability of hospital mortality based on physiological variables measured during the first 24 hours of ICU admission. It incorporates 17 parameters: 12 physiological variables, age, type of admission, and three underlying disease variab
Simplified Acute Physiology Score II SAPS II Explanation and Clinical Context The SAPS II score is a validated severity of illness classification intended to estimate risk of hospital death for adult patients admitted to intensive care units using the worst values collected in the first 24 hours after admission. The score aggregates points from 15 items including age type of admission heart rate systolic blood pressu
Sarcoidosis Cardiac Involvement Score (SCIS): Explanation and Clinical Context The SCIS is a scoring system designed to assess the likelihood of cardiac involvement in patients with sarcoidosis. It incorporates clinical and imaging parameters to stratify risk and guide management decisions. A higher score indicates a greater likelihood of cardiac involvement and may necessitate more aggressive monitoring and treatmen
ECG Pattern -- choose -- Normal Nonspecific repolarization changes Typical for myocarditis (diffuse ST-T changes / PR depression / new AV block / ventricular arrhythmia) CMR (2018 Lake Louise Criteria) -- choose -- Positive Equivocal / indeterminate Negative Not performed Days from Symptom Onset to CMR (leave blank if CMR not done) SARS-CoV-2 Myocarditis: Explanation and Clinical Context In patients with COVID-19, my
SAVE Post-MI LV Dysfunction Prognostic Score — Explanation and Clinical Context This calculator estimates the prognosis of patients after myocardial infarction (MI) with left ventricular (LV) systolic dysfunction, using key clinical and laboratory parameters repeatedly shown to correlate with mortality and adverse remodeling. The variables include age, LVEF, Killip class, renal function, systolic blood pressure, hear
SAVE Score (Survival After Veno-Arterial ECMO): Explanation and Clinical Context The SAVE score is a validated tool designed to predict in-hospital mortality for adult patients undergoing VA-ECMO for refractory cardiogenic shock. It incorporates multiple pre-ECMO variables, including age, body weight, underlying diagnosis, pre-ECMO organ failures, serum bicarbonate, peak inspiratory pressure, and duration of mechanic
SC (Subcostal View) SC 4C (Subcostal 4 Chamber) 4C : 4 chamber, IAS : Interatrial septum, IVS : Interventricular septum, LA : Left atrium, LV : Left ventricle, MV : Mitral valve, RA : Right atrium, RV : Right ventricle, SC : Subcostal, TV : Tricuspid valve. SC (Superior Vena Cava) IVC : Inferior vena cava, RA : Right atrium, SC : Subcostal, SVC : Superior vena cava. SC (Long Axis IVC) IVC : Inferior vena cava, RA : R
SCAI Shock Stages: Explanation and Clinical Context The Society for Cardiovascular Angiography and Interventions (SCAI) shock stages provide a standardized framework for classifying the severity of cardiogenic shock from Stage A (At risk) to Stage E (Extremis). Stage A includes patients at risk but without hypoperfusion. Stage B shows early signs of shock without organ dysfunction. Stage C represents classic cardioge
: Explanation and Clinical Context The Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) evaluated the role of implantable cardioverter-defibrillator (ICD) therapy in patients with heart failure and reduced ejection fraction (HFrEF). The study enrolled patients with ischemic or nonischemic cardiomyopathy, NYHA class II–III, and LVEF ≤35%. This calculator provides an approximate estimation of the 3-year all-cause
SCD-HeFT Risk Model: Explanation and Clinical Context The SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial) Risk Model estimates 5-year mortality risk in patients with chronic heart failure and reduced ejection fraction. The model is derived from a multivariable Cox proportional hazards analysis of the SCD-HeFT trial population, incorporating age, sex, NYHA class, left ventricular ejection fraction (LVEF), ische
SCD-HeFT Risk Model: Explanation and Clinical Context The SCD-HeFT Risk Model estimates the 5-year risk of all-cause mortality in patients with heart failure with reduced ejection fraction (HFrEF) who are candidates for implantable cardioverter-defibrillator (ICD) therapy. The model uses clinical variables available at baseline, including age, NYHA functional class, left ventricular ejection fraction (LVEF), presence
Schwartz Score for Long QT Syndrome: Explanation and Clinical Context The Schwartz Score is a validated diagnostic tool to assess the probability of congenital Long QT Syndrome (LQTS). It incorporates electrocardiographic, clinical, and family history features including QTc interval, history of syncope, congenital deafness, and family history of sudden cardiac death or LQTS. Points are assigned based on QTc duration,
SCN5A Variant Pathogenicity Index: Explanation and Clinical Context The SCN5A Variant Pathogenicity Index is a clinically validated tool to estimate the likelihood that a given SCN5A gene variant contributes to arrhythmia disorders, including Brugada Syndrome and Long QT Syndrome type 3. It integrates multiple lines of evidence: variant type (missense, nonsense, frameshift, splice-site, in-frame indel), functional st
SCORE-Hyper Model: Explanation and Clinical Context SCORE-Hyper is a validated tool designed to estimate the 10-year risk of fatal cardiovascular events in patients with hypertension. It considers key variables including age, sex, systolic blood pressure, total cholesterol, and smoking status. The model incorporates coefficients specifically derived from hypertensive populations, providing more precise risk predictio
About SCORE2 (European Society of Cardiology, 2021): SCORE2 is the updated cardiovascular risk estimation model replacing the original SCORE (2003). It predicts the 10-year risk of both fatal and non-fatal cardiovascular events in apparently healthy adults aged 40-69 years. Developed using pooled European cohort data (n = > 600,000), it includes sex, age, smoking status, systolic blood pressure, and lipid profile (to
SCORED Trial (Sotagliflozin) Risk Index — explanation and clinical context This calculator implements a trial-derived risk estimator based on SCORED trial aggregate results. SCORED enrolled adults with type 2 diabetes and chronic kidney disease and reported a primary composite event rate in the placebo arm of approximately 7.5 events per 100 patient-years (≈7.5% per year) and an estimated hazard ratio of 0.74 for the
SCORTEN Severity of Illness Score for Toxic Epidermal Necrolysis SCORTEN is a validated prognostic index intended to estimate the probability of death in patients with Stevens Johnson syndrome and toxic epidermal necrolysis when assessed within the first 24 hours of admission. The score comprises seven independent variables each scored as one point if present. These variables are age 40 years or older, presence of ac
Screening ECG Yield in Primary Care: Explanation and Clinical Context The Screening ECG Yield in Primary Care calculator estimates the Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of routine electrocardiographic (ECG) screening programs based on population disease prevalence and test characteristics (sensitivity and specificity). PPV and NPV are essential for evaluating the clinical yield of sc
Seattle Angina Questionnaire (SAQ): Explanation and Clinical Context The SAQ is a patient-reported outcome measure specifically developed to quantify the impact of angina on patients with coronary artery disease. It assesses five domains: Physical Limitation, Angina Stability, Angina Frequency, Treatment Satisfaction, and Quality of Life, each scored from 0 (worst) to 100 (best). Higher scores indicate better patient
Seattle Heart Failure Model (SHFM): Explanation and Clinical Context The SHFM is a validated multivariable model to estimate mortality risk in patients with chronic heart failure based on clinical, laboratory, and treatment variables. It was developed using data from the PRAISE I cohort and externally validated in multiple populations. The model calculates a risk score (SHFM Score) using regression coefficients appli
Seattle Heart Failure Model (SHFM): Explanation and Clinical Context The SHFM is a validated multivariable model to estimate mortality risk in patients with chronic heart failure based on clinical, laboratory, and treatment variables. It was developed using data from the PRAISE I cohort and externally validated in multiple populations. The model calculates a risk score (SHFM Score) using regression coefficients appli
Seattle Proportional Risk Model (SPRM): Explanation and Clinical Context The SPRM is a prognostic tool designed to estimate the proportion of sudden death among all-cause mortality in patients with heart failure and reduced ejection fraction (EF < 35%). Developed from a cohort of 9,885 patients with 2,552 deaths, the model identifies key clinical variables associated with a higher likelihood of sudden death. These in
Explanation and Clinical Context This tool provides an estimation of mortality severity in patients presenting with sepsis by integrating several physiologic and biochemical variables that are strongly associated with adverse outcomes. Serum lactate reflects cellular hypoperfusion and metabolic stress. Mean arterial pressure reflects circulatory stability and correlates with the adequacy of organ perfusion. Creatinin
Sepsis-Related Myocardial Dysfunction (SIMD) Severity Index Enter values available at bedside/ICU admission or within the first 24 hours. Use absolute (positive) value for GLS (e.g., 18 = normal strain ~ −18%). Troponin input is expressed as multiple of your lab’s upper limit of normal (ULN). Norepinephrine dose is in µg/kg/min. Sepsis-Related Myocardial Dysfunction (SIMD): Explanation and Clinical Context SIMD (ofte
Explanation and Clinical Context This tool translates guidance from the twenty twenty five American College of Cardiology and American Heart Association guideline for acute coronary syndromes into a structured approach to repeat twelve lead electrocardiograms in patients with suspected or confirmed acute coronary syndrome. The guideline recommends acquisition and interpretation of an ECG within ten minutes of first m
Serial Troponin Trajectory Interpretation. Comprehensive Explanation and Clinical Context Serial measurement of high sensitivity cardiac troponin plays a pivotal role in the diagnosis of acute coronary syndrome. The 2025 AHA ACS guideline emphasizes rapid rule in and rule out assessment using baseline and 1 to 2 hour repeat hs troponin values combined with clinical history and ECG findings. Serial trajectory interpre
Serum Lactate Mortality Index (post-CPB): Explanation and Clinical Context The Serum Lactate Mortality Index (SLMI) is a prognostic tool used to estimate the risk of postoperative mortality in patients after cardiopulmonary bypass (CPB). It is calculated by multiplying peak serum lactate levels (mmol/L) by the time elapsed since CPB (hours). Elevated lactate levels reflect impaired tissue perfusion and oxygen deliver
Sodium Na mEqL Glucose mgdL BUN mgdL Explanation and Clinical Context Serum osmolality reflects the concentration of dissolved particles in plasma and provides an essential window into the body water balance. The major contributors to serum osmolality are sodium glucose and blood urea nitrogen which form the basis of the widely used calculated osmolality formula. Normal serum osmolality ranges from two hundred sevent
Left atrium (Size) Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the ASE and EACVI (2015) Left atrium (Volume) Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the ASE and EACVI (2015) Right atrium (Size) Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the ASE and EACVI (
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SF-36 Physical Function Domain: Explanation and Clinical Context The SF-36 Physical Function (PF) domain evaluates the extent to which health limits physical activities, from vigorous activities such as running or lifting heavy objects to basic self-care tasks. It consists of 10 items, each scored on a Likert scale. The total raw score is converted to a 0–100 scale, where higher scores indicate better physical functi
SGLT2 Benefit Probability Score: Explanation and Clinical Context The SGLT2 Benefit Probability Score is designed to estimate the likelihood of clinical benefit from SGLT2 inhibitors in patients with heart failure (HF), chronic kidney disease (CKD), and/or diabetes mellitus (DM). This tool incorporates key clinical variables such as age, presence of HF, CKD, and DM. Higher scores indicate a greater predicted benefit
Shanghai Score for Brugada Syndrome: Explanation and Clinical Context The Shanghai Score is a diagnostic scoring system developed to assess the likelihood of Brugada Syndrome based on clinical, electrocardiographic, familial, and genetic criteria. It assigns weighted points to spontaneous Type 1 ECG, fever-induced or drug-provoked Type 1 ECG, documented ventricular arrhythmias, family history of sudden cardiac death,
SHARE-FI (Frailty Index in Elderly Cardiac Patients): Explanation and Clinical Context SHARE-FI is a validated tool designed to assess frailty in community-dwelling older adults, particularly useful in elderly cardiac patients. It uses five domains: exhaustion, loss of appetite, weakness (grip strength), slowness (walking speed), and low physical activity. Each domain contributes to a composite score that classifies
: Rationale, Model Choices, and Clinical Context This calculator estimates relative cardiometabolic risk multipliers associated with shift work using pooled quantitative effects from large meta-analyses. For cardiovascular disease (CVD) outcomes, a contemporary dose–response meta-analysis showed that night-shift workers have a higher risk of total CVD events (RR ≈ 1.13) and CVD mortality (RR ≈ 1.27); risk rises with
Shock Index (HR/SBP Ratio): Explanation and Clinical Context The Shock Index (SI) is a simple, bedside physiological ratio calculated by dividing the heart rate (HR) by the systolic blood pressure (SBP). It serves as a rapid and sensitive indicator of hemodynamic compromise and circulatory shock. A normal Shock Index typically ranges from 0.5 to 0.7. Values above 0.9 are considered abnormal and have been strongly cor
SHOCK Score: Explanation and Clinical Context The SHOCK Score was developed from the SHOCK Trial Registry to predict short-term mortality among patients presenting with cardiogenic shock following acute myocardial infarction. This score integrates seven readily available clinical variables: age > 75 years, female gender, anterior myocardial infarction, previous MI, serum creatinine > 1.9 mg/dL, altered mental status,
SHOCKED Score: Explanation and Clinical Context The SHOCKED Score is a clinical tool developed to predict long-term survival in patients with implantable cardioverter-defibrillators (ICDs). It incorporates several clinical variables to stratify patients into different risk categories. A higher score indicates a higher risk of mortality, guiding clinicians in decision-making regarding device therapy and management str
Explanation and Clinical Context This tool is designed for patients with acute coronary syndromes who have undergone percutaneous coronary intervention with contemporary drug eluting stents and are treated with dual antiplatelet therapy that combines aspirin and an oral P2Y12 inhibitor. The 2025 acute coronary syndromes guideline identifies a default strategy of about 12 months of dual antiplatelet therapy in patient
Short Nutritional Assessment Questionnaire (SNAQ): Explanation and Clinical Context SNAQ is a validated screening tool to quickly assess the risk of malnutrition in adults, especially elderly patients or those with chronic illness. It evaluates three key parameters: appetite loss, recent unintentional weight loss, and use of supplemental drinks or tube feeding. Each response is scored, and the total SNAQ score indica
Shunt Fraction Index (Qp:Qs Ratio): Explanation and Clinical Context The Qp:Qs ratio, also known as the Shunt Fraction Index, is used to quantify the magnitude of left-to-right cardiac shunts. It is defined as the ratio of pulmonary blood flow (Qp) to systemic blood flow (Qs). A Qp:Qs ratio of 1 indicates no shunt, while values above 1 indicate a left-to-right shunt, with higher values reflecting larger shunts. Clini
Signal-Averaged QRS Duration: Explanation and Clinical Context Signal-Averaged QRS (SA-QRS) duration is a specialized ECG measurement designed to detect subtle conduction abnormalities that predispose patients to ventricular arrhythmias. It is typically performed using high-resolution ECG recordings and computer averaging to reduce noise. Normal SA-QRS duration is generally less than 114 ms. Values between 114–120 ms
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Simpson’s biplane method: explanation, clinical context and references The biplane method of disks (the modified Simpson’s rule) estimates left ventricular end-diastolic and end-systolic volumes from apical 4-chamber and apical 2-ch views; the ejection fraction (LVEF) is then calculated as EF = [(EDV − ESV) / EDV] × 100%. In routine practice the machine may report volumes from each apical view and clinicians commonly
Single Antiplatelet Therapy Transition for High Bleeding Risk: Explanation and Clinical Context Transition from dual antiplatelet therapy to single antiplatelet therapy is supported in the management of high bleeding risk patients after percutaneous coronary intervention according to the AHA ACS Guideline 2025. For patients with elevated bleeding tendency a shorter DAPT duration is reasonable and may safely reduce he
Single Sample hs Troponin Evaluation ≥3 Hours Symptom: Explanation and Clinical Context High sensitivity cardiac troponin is the preferred biomarker for evaluating suspected acute coronary syndrome. AHA 2025 guideline states that hs Troponin allows earlier rule out or rule in of myocardial infarction. When evaluating a patient who presents at least three hours from symptom onset a single hs Troponin below the assay s
Temperature Celsius Heart Rate bpm Respiratory Rate PaCO2 mmHg White Blood Cell Count x10⁹ per L Band Form Percentage Explanation and Clinical Context SIRS describes a widespread inflammatory response of the body to internal or external stressors. It is defined by abnormalities in temperature heart rate respiratory rate PaCO2 and white blood cell count including increased immature neutrophil band forms. The criteria
SITS-ICH Score: Explanation and Clinical Context The SITS-ICH Score is a validated clinical tool designed to predict the risk of symptomatic intracranial hemorrhage (sICH) following intravenous thrombolysis with alteplase in patients with acute ischemic stroke. Developed from the SITS-MOST registry, it uses baseline demographic and clinical variables to provide an individualized estimate of hemorrhagic risk. The scor
Siu Predictive Model: Explanation and Clinical Context The Siu Predictive Model estimates the risk of maternal cardiac events during pregnancy in women with pre-existing heart disease. It incorporates key clinical predictors: NYHA functional class III–IV, history of heart failure, presence of left heart obstruction, and previous cardiac events. Each predictor is assigned a weight, and the sum produces a total score t
Six CIT Dementia Screening Tool Explanation and Clinical Context The Six CIT Dementia Screening Tool offers a brief cognitive assessment that is practical for primary care settings. It evaluates orientation, working memory, and attention using six simple tasks that can be administered rapidly without the need for special equipment. The scoring system assigns weighted values to each item, creating a total score range
SLEDAI Lupus Activity Score Explanation and Clinical Context SLEDAI is a validated global index used to quantify disease activity in patients with systemic lupus erythematosus. It evaluates clinical and laboratory findings that reflect inflammatory activity over the preceding ten days. The score incorporates neurological involvement renal manifestations mucocutaneous changes musculoskeletal signs serologic activity a
SLUMS Cognitive Test Explanation and Clinical Context The Saint Louis University Mental Status Examination is a cognitive screening tool used to identify early cognitive decline and neurocognitive disorders. It evaluates multiple domains that include orientation memory attention executive function visuospatial ability and delayed recall. The test is sensitive for detecting mild neurocognitive disorder which may not b
— explanation and clinical context This tool classifies heart failure patients into subpopulations using commonly accepted left ventricular ejection fraction thresholds (HFrEF <41%, HFmrEF 41–49%, HFpEF ≥50%). It then provides directional prognostic information using two well-known validated frameworks as proxies: the MAGGIC risk framework for 1- and 3-year mortality, and the GWTG-HF model for in-hospital mortality r
Smoking Cessation Cardiac Event Reduction Model: Explanation and Clinical Context Smokers who quit experience a rapid decline in cardiovascular risk within the first few years, with heavy smokers (≥20 pack-years) achieving approximately a 39% lower risk of incident cardiovascular disease by 5 years compared with those who continue to smoke (hazard ratio ~0.61). Risk continues to decline more gradually over the follow