1,329 calculators and references across 60 specialties, with formula confidence shown up front.
Absolute and Relative Risk Reduction Explanation and Clinical Context Absolute Risk Reduction ARR represents the difference in event rates between a control group and an experimental group. ARR quantifies how much an intervention reduces risk in absolute terms and is directly interpretable in clinical practice. Relative Risk Reduction RRR represents the proportional decrease in risk relative to the baseline risk of t
ACEF Score: Explanation and Clinical Context The ACEF Score (Age, Creatinine, and Ejection Fraction) is a simple, validated risk prediction tool for short-term mortality in patients undergoing cardiac surgery or coronary interventions. It is calculated using the formula: ACEF = Age / LVEF + 1 (if serum creatinine > 2 mg/dL). Higher scores indicate higher risk of adverse outcomes. It is particularly useful in preopera
AFEQT Score (Atrial Fibrillation Effect on Quality of Life): Explanation and Clinical Context The AFEQT Score is a validated patient-reported outcome measure that assesses health-related quality of life in patients with atrial fibrillation (AF). It evaluates four domains: Symptoms, Daily Activities, Treatment Concern, and Overall Health. Each domain is scored from 0 to 100, where higher scores indicate better quality
Ankle Brachial Index For PAD Risk. Clinical Explanation and Context The Ankle Brachial Index is a simple and validated noninvasive test used to detect the presence and severity of peripheral artery disease. It is calculated by dividing the systolic blood pressure at the ankle by the highest systolic blood pressure measured in both arms. ABI provides an objective assessment of lower extremity perfusion and correlates
Aortic Aneurysm Expansion Index (AAEI): Explanation and Clinical Context The Aortic Aneurysm Expansion Index (AAEI) quantifies the annual relative increase in aortic diameter, expressed as a percentage per year. It is calculated using the formula: (Follow-up Diameter - Baseline Diameter) / (Baseline Diameter × Time Interval) × 100%. AAEI helps clinicians identify patients at risk of rapid aneurysm growth and potentia
Aortic Compliance Index (ACI): Explanation and Clinical Context The Aortic Compliance Index (ACI) represents the ability of the aorta to expand and contract with each cardiac cycle in response to changes in blood pressure. It reflects the elastic properties of the aortic wall and serves as a surrogate marker of arterial stiffness. The formula used is: ACI = Stroke Volume / Pulse Pressure where Stroke Volume (SV) is t
Aortic Stiffness Index (ASI): Explanation and Clinical Context The Aortic Stiffness Index (β) is a non-invasive echocardiographic measure of the intrinsic stiffness of the ascending aorta. It reflects the mechanical properties of the aortic wall and is calculated using systolic and diastolic blood pressures and the corresponding aortic diameters. An increased ASI indicates reduced aortic compliance and is associated
Aortic Valve Area by Continuity Equation: Explanation and Clinical Context Aortic valve area is a fundamental parameter used to assess the severity of aortic stenosis. The continuity equation is the most widely endorsed method for calculating aortic valve area because it is grounded in the principle of conservation of mass. According to this principle, flow in the left ventricular outflow tract must equal flow across
Apical HCM Index: Explanation and Clinical Context The Apical HCM Index is a simple echocardiographic metric calculated as the ratio of maximal apical wall thickness to the left ventricular end-diastolic diameter (LVEDD). It was first described by Kobayashi et al. to identify patients with apical hypertrophic cardiomyopathy (HCM), particularly in populations where this variant is more prevalent, such as in Japan. An
ApoB/ApoA1 Ratio: Explanation and Clinical Context The ApoB/ApoA1 ratio is a validated biomarker reflecting the balance between atherogenic and anti-atherogenic lipoproteins. ApoB represents the total number of atherogenic particles (including LDL, VLDL), while ApoA1 is the main protein in HDL, which is protective. A higher ApoB/ApoA1 ratio indicates a predominance of atherogenic lipoproteins and a higher risk for ca
Atherogenic Index of Plasma (AIP): Explanation and Clinical Context The Atherogenic Index of Plasma (AIP) is calculated as the base-10 logarithm of the ratio of plasma triglycerides (TG) to high-density lipoprotein cholesterol (HDL-C) in mmol/L: log10(TG/HDL-C). It serves as a sensitive marker of plasma atherogenicity and is closely associated with the size of LDL particles, with higher AIP indicating a predominance
Explanation and Clinical Context Attack rate is an epidemiologic measure used to quantify the proportion of individuals in a population who develop a condition during an outbreak period. It is commonly used in infectious disease investigations to describe the speed and extent of disease spread within a defined group. The calculation compares the number of new cases with the number of individuals who are susceptible o