Clinical Guides And Calculator Articles
Evidence-based medical calculator guides, clinical scoring tutorials, and decision-support articles from the Quick Medical Calculator editorial team.
All articles
CHA2DS2-VASc Score: Stroke Risk and Anticoagulation in Atrial Fibrillation
CHA2DS2-VASc identifies which atrial fibrillation patients need anticoagulation. Score 0 (men) or 1 (women, sex point only) = low risk; no anticoagulation. Score 2+ (men) or 3+ (women) = anticoagulation recommended. DOACs preferred over warfarin in non-valvular AF.
DAS28: Rheumatoid Arthritis Disease Activity Score Guide
The Disease Activity Score in 28 Joints (DAS28) quantifies RA disease activity using tender joint count, swollen joint count, patient global health, and ESR or CRP. DAS28 <2.6 = remission; 2.6–3.2 = low disease activity; >5.1 = high. It is the cornerstone of treat-to-target strategy.
Ottawa Ankle and Knee Rules: When to X-Ray in the ED
The Ottawa Ankle Rules and Ottawa Knee Rule are bedside clinical decision instruments that safely identify which ankle and knee injuries require radiography. Properly applied, they have near-100% sensitivity for clinically significant fractures while reducing unnecessary X-rays by 30–40%.
Centor and McIsaac Score: Strep Throat Diagnosis and Antibiotic Stewardship
Centor score predicts GAS pharyngitis probability using 4 clinical criteria. McIsaac adds age adjustment. Score 0–1 = no testing needed; 2–3 = RADT; ≥4 = RADT or empirical treatment. Neither score should drive antibiotic prescriptions alone — RADT confirmation is the evidence-based bridge.
Caprini VTE Risk Score: Surgical Thromboprophylaxis Guide
The Caprini Risk Assessment Model (RAM) stratifies perioperative VTE risk using 40+ patient- and procedure-specific factors. Caprini 0 = very low; 1–2 = low; 3–4 = moderate; ≥5 = high. VTE is preventable — the Caprini score turns 'should we prophylax?' into a data-driven decision.
AUDIT and AUDIT-C: Alcohol Use Screening in Clinical Practice
The Alcohol Use Disorders Identification Test (AUDIT) is the WHO-endorsed gold standard for detecting hazardous and harmful alcohol use. AUDIT score ≥8 = hazardous/harmful use; ≥20 = likely dependence. AUDIT-C ≥3 (women) or ≥4 (men) triggers full AUDIT.
Endocrinology Calculators Spotlight: TSH, Free T4, HOMA-IR, and Thyroid Nodule Tools
Endocrinology is one of the most calculator-dense specialties in medicine. This spotlight covers six essential tools: TSH/free T4 interpretation, subclinical hypothyroidism management thresholds, TI-RADS thyroid nodule risk scoring, corrected calcium, HOMA-IR, and the FRAX fracture risk tool.
Bishop Score: Labor Induction and Cervical Ripening Guide
The Bishop score quantifies cervical readiness for labor induction across five parameters: dilation, effacement, station, consistency, and position. Score ≥8 = favorable cervix; proceed directly to oxytocin. Score <6 = unfavorable; cervical ripening agent first.
Revised Cardiac Risk Index: Perioperative Risk Assessment Guide
The Revised Cardiac Risk Index (RCRI) stratifies cardiac risk before noncardiac surgery using 6 clinical variables. RCRI 0 = <1% MACE risk; RCRI ≥3 = ~5% or higher. Adding perioperative high-sensitivity troponin surveillance provides incremental prognostic benefit beyond RCRI alone.
FRAX Score: Fracture Risk Assessment and Osteoporosis Management
FRAX calculates 10-year probability of major osteoporotic fracture (MOF) and hip fracture using 12 clinical risk factors with or without bone mineral density. A FRAX-based treat threshold of ≥20% MOF or ≥3% hip fracture is widely used in the US. FRAXplus (2024) addresses several limitations.
HOMA-IR: Insulin Resistance Assessment in Clinical Practice
HOMA-IR uses fasting glucose and fasting insulin to estimate insulin resistance. General reference: HOMA-IR >2.5–3.0 suggests insulin resistance in most Western populations; >3.6–4.0 suggests significant IR associated with metabolic complications. Always interpret in clinical context.
Glasgow-Blatchford Score: Upper GI Bleeding Triage Guide
The Glasgow-Blatchford Score (GBS) is the best validated tool for identifying low-risk upper GI bleeding (UGIB) patients safe for outpatient management. GBS ≤2 has a negative predictive value of ~98% for the need for endoscopic intervention — roughly 20–25% of UGIB presentations. GBS is the preferred triage score for safe discharge decisions; Rockall is superior for predicting in-hospital mortality.
NIHSS Score: National Institutes of Health Stroke Scale Guide
The NIHSS is the global standard for quantifying acute stroke severity across 15 neurological domains. Score 0 = normal; ≥25 = very severe. It predicts 3-month functional outcomes, guides tPA and thrombectomy eligibility, and tracks treatment response. Key limitation: it systematically underestimates posterior circulation strokes — a patient with basilar artery occlusion can score just 2–4 while having a life-threatening deficit. Know the scale. Know its blind spots.
Wells Criteria for Pulmonary Embolism: Complete Clinical Guide
Master the Wells Criteria for Pulmonary Embolism: scoring, two-tier vs three-tier interpretation, D-dimer integration, validation evidence, and how it compares to Geneva and PERC.
Nephrology Calculators Spotlight: eGFR, FENa, UACR, and AKI Staging
Kidney disease touches every specialty. This spotlight covers five essential nephrology calculators: CKD-EPI eGFR (chronic function), FENa (AKI differentiation), urine albumin-creatinine ratio (early injury/proteinuria), KDIGO AKI staging (acute severity), and Cockcroft-Gault (drug dosing). Know when to use each — and when not to.
FENa and Urine Sodium: AKI Differential Diagnosis Guide
FENa <1% suggests prerenal AKI (tubular sodium reabsorption intact); FENa ≥1% suggests intrinsic renal injury. Meta-analysis confirms sensitivity 90%, specificity 82% in ideal conditions. Both drop significantly in patients on diuretics — use FEUrea instead. Always interpret FENa in the full clinical context.
Atrial Fibrillation Management: CHA2DS2-VASc in Clinical Practice
Atrial fibrillation affects over 50 million people globally and accounts for one in three ischemic strokes. Guideline-adherent anticoagulation — driven by CHA2DS2-VASc — reduces stroke risk by up to 64%. Real-world data confirm that adherent OAC significantly cuts mortality and stroke vs no treatment. Know the score. Treat the score.
qSOFA Score and Sepsis-3: Complete Clinical Guide
qSOFA (altered mentation, RR ≥22, SBP ≤100) was introduced with Sepsis-3 as a bedside prompt to identify patients with suspected infection at risk of poor outcomes outside the ICU. Score ≥2 predicts 3–14× higher mortality across risk strata. qSOFA is NOT a sepsis diagnostic criterion — it's a prompt to investigate further. SOFA ≥2 in a patient with suspected infection defines sepsis.
MELD Score and Child-Pugh: Liver Disease Severity Guide
MELD (Model for End-Stage Liver Disease) uses bilirubin, INR, and creatinine to predict 3-month mortality in cirrhosis and drives organ allocation in the US. MELD-Na adds serum sodium and is now the US standard for transplant listing. Child-Pugh uses five parameters (some subjective) to classify severity as A/B/C. Both tools are essential; neither tells the full story alone.
CKD-EPI 2021 eGFR Equation: Complete Clinical Guide
The 2021 CKD-EPI equation is now the standard for estimating GFR in adults. It removed the race variable from the 2009 equation following recognition that using race as a biological proxy introduced systematic bias. Performance is similar to the 2009 equation in most populations. eGFR <60 mL/min/1.73 m² for ≥3 months = CKD. For high-stakes decisions (drug dosing, transplant workup), confirm with cystatin C–based eGFR or measured GFR.
Pneumonia Severity: CURB-65 vs PSI/PORT — Choosing the Right Tool
CURB-65 is faster and simpler — 5 bedside variables, ideal for ED triage. PSI/PORT uses 20 variables and a two-step process, but more accurately identifies truly low-risk patients safe for outpatient treatment. Neither tool alone should drive admission decisions — use them with clinical judgment and IDSA/ATS minor criteria for ICU thresholds. In elderly patients, PSI has better discrimination than CURB-65.
CURB-65 Score: Complete Clinical Guide
CURB-65 is a 5-point bedside severity score for community-acquired pneumonia: Confusion, Urea >7 mmol/L, Respiratory rate ≥30, Blood pressure (systolic <90 or diastolic ≤60), and age ≥65. Score 0–1 = low mortality (<3%), suitable for outpatient treatment.
PHQ-9 Depression Screening: Complete Clinical Guide
The PHQ-9 is a 9-item self-report questionnaire based directly on DSM-IV major depression criteria. Each item is scored 0–3; the total ranges 0–27. A score ≥10 has 88% sensitivity and 88% specificity for major depressive disorder.
Cardiology Calculators: Essential Clinical Tools
Five calculators drive most cardiology risk decisions: CHA2DS2-VASc for AF stroke risk, HAS-BLED for bleeding risk before anticoagulation, HEART Score for chest pain triage, Framingham for 10-year cardiovascular risk, and ASCVD for statin therapy decisions.
APACHE II Score: Complete Clinical Guide
APACHE II quantifies ICU illness severity using 12 acute physiologic variables, age, and chronic health status (range 0–71). It predicts group mortality — not individual outcome. Most accurate when calculated within the first 24 hours of ICU admission using the worst values.
PE Workup: Wells vs Geneva vs PERC — Which to Use When
Use PERC first in low-acuity patients with low gestalt for PE — if all 8 criteria are absent, PE is excluded without D-dimer or imaging. For patients who fail PERC, apply Wells or Revised Geneva to determine pretest probability, then pair with D-dimer.
Wells Score for DVT: Complete Clinical Guide
The Wells Score stratifies patients with suspected DVT into low, moderate, or high pretest probability using nine clinical criteria. Combined with D-dimer testing, it safely rules out DVT in low-probability patients without ultrasound.
Glasgow Coma Scale: Complete Clinical Guide
The GCS quantifies level of consciousness across three domains — eye opening (1–4), verbal response (1–5), and motor response (1–6) — yielding a total of 3–15. Scores ≤8 define severe impairment and typically indicate the need for airway protection. Report individual components, not just the sum.
Risk Stratification in Chest Pain: HEART vs TIMI vs GRACE
Compare the three major risk scores for acute coronary syndromes. Learn when to use HEART, TIMI, and GRACE scores in clinical practice.
The Complete Guide to CHA₂DS₂-VASc Score
Master the CHA₂DS₂-VASc score for atrial fibrillation stroke risk stratification. Learn when to anticoagulate and how to apply evidence-based guidelines.
SOFA Score in Sepsis: What Every Intensivist Needs to Know
Understanding the Sequential Organ Failure Assessment (SOFA) score for sepsis diagnosis and prognosis. Learn qSOFA screening and organ dysfunction criteria.
Evidence Update: CKD-EPI 2021 vs MDRD GFR Equations
The new race-free CKD-EPI 2021 equation replaces both the CKD-EPI 2009 and MDRD equations. Here's what clinicians need to know about the transition.
Nutrition Calculators: From BMI to Caloric Needs
Master essential nutrition calculations including BMI, BMR, TDEE, and macronutrient distribution for clinical nutrition assessment.
Pediatric Calculators: Essential Tools for Every Pediatrician
From growth percentiles to dosing calculations, discover the must-have pediatric calculators for daily practice.
How to Interpret ABG Results: A Clinical Framework
Master arterial blood gas interpretation with this systematic approach to acid-base disorders.
Understanding the MELD Score: A Complete Guide
Learn how to interpret and apply the MELD score for liver disease severity assessment and transplant prioritization.
Emergency Medicine: 10 Essential Calculators Every ER Physician Needs
A curated list of the most critical clinical calculators for emergency medicine practice, from risk stratification to treatment decisions.