San Francisco Syncope Rule (SFSR) Calculator
The San Francisco Syncope Rule (SFSR) is a clinical decision rule that identifies patients with syncope at high risk for serious 30-day outcomes. It uses 6 clinical predictors to stratify risk in the emergency department setting.
About
The San Francisco Syncope Rule (SFSR) was developed by Dr. Quinn and colleagues at the University of California, San Francisco, and published in Annals of Emergency Medicine in 2004. The rule was derived from a cohort of 791 patients presenting to the ED with syncope or near-syncope. It identifies patients at risk for serious 30-day outcomes including death, myocardial infarction, arrhythmia, pulmonary embolism, stroke, subarachnoid hemorrhage, significant hemorrhage, or recurrent syncope leading to hospitalization. The original rule used 5 criteria (abnormal ECG, dyspnea, hematocrit <30%, systolic BP <90, history of CHF), while subsequent validation studies expanded to include age >65 as a sixth criterion. When any single criterion is present, the sensitivity for detecting serious outcomes is approximately 96-98%, with a specificity of about 56-62%. A negative SFSR (no criteria present) confers a <1% risk of serious 30-day outcome, making it a useful rule-out tool. The SFSR is endorsed by the American College of Emergency Physicians (ACEP) clinical policy for syncope.
Formula
Age >65 + Systolic BP <90 + History of CHF + Abnormal ECG + Hematocrit <30% + Dyspnea
The SFSR is positive if any one of the six clinical predictors is present. Each predictor is scored as 0 (absent) or 1 (present). A total score ≥1 indicates high risk for a serious 30-day outcome (approximately 11% incidence). A score of 0 (no predictors present) indicates low risk (approximately 0.6% incidence). Age >65 years recognizes that advanced age independently increases the probability of cardiac and non-cardiac serious outcomes. Systolic BP <90 mmHg at triage identifies hemodynamic instability. History of congestive heart failure suggests underlying structural heart disease. Abnormal ECG includes any new changes (ischemia, arrhythmia, pacemaker malfunction) or non-sinus rhythm. Hematocrit <30% (or hemoglobin <10 g/dL) identifies significant anemia that may have precipitated syncope. Dyspnea (shortness of breath) preceding or accompanying syncope may suggest pulmonary embolism or cardiac ischemia.
Score Interpretation
Syncope accounts for 1-3% of all ED visits and up to 6% of hospital admissions. The SFSR helps clinicians identify which syncope patients require hospital admission versus those who can be safely discharged. A negative SFSR (no criteria met) has a negative predictive value of >99% for serious 30-day outcomes. The SFSR has been validated in multiple international ED populations with consistent sensitivity of 89-98%, though specificity varies (41-63%). It is one of the most widely studied syncope clinical decision rules and is incorporated in the ACEP clinical policy for syncope management. Key limitations include its lower specificity leading to potentially unnecessary admissions, and reduced accuracy in patients with syncope mimics (seizure, hypoglycemia, stroke). The rule is best applied to patients with syncope as the primary presenting complaint, not as an incidental finding. The CHESS study also identified that patients with a negative SFSR plus a normal BNP and normal troponin have an even lower risk, suggesting combined strategies may improve specificity.
SFSR Negative — Low Risk — 0–0
30-day serious outcome risk: 0.6%. Safe for outpatient management.
Management: May consider discharge from ED with appropriate follow-up. Reassess if new symptoms develop.
SFSR Positive — High Risk — 1–6
30-day serious outcome risk: approximately 11%. Hospital admission recommended.
Management: Admit for observation and further diagnostic evaluation. Consider echocardiogram, cardiac monitoring, and telemetry. Evaluate for PE if dyspnea present.
Reference Ranges
| Population | Normal Range | Notes |
|---|---|---|
| Adult ED patients presenting with syncope or near-syncope | 0 (low risk) to 6 (high risk) | Any positive criterion indicates high risk. Score 0 = SFSR negative. |
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A 72-year-old woman presents to the ED after a witnessed syncopal episode at a grocery store. She reports feeling short of breath before passing out. Vital signs: BP 88/56 mmHg, HR 88. ECG shows atrial fibrillation (new onset). Hct: 28%. She has a history of CHF (ejection fraction 40%). SFSR: Age >65 (yes, +1), SBP <90 (yes, +1), CHF history (yes, +1), Abnormal ECG (yes, +1), Hct <30% (yes, +1), Dyspnea (yes, +1). Score: 6/6 — SFSR positive, high risk for serious 30-day outcome. Admitted for telemetry, echocardiogram, and further management.
Related Conditions
Common Mistakes
Applying SFSR to patients with syncope mimics (seizure, hypoglycemia, stroke, head trauma)
SFSR is validated only for patients with syncope or near-syncope as the primary presentation. Do not use for seizure, hypoglycemia, or other altered mental status causes.
Interpreting any abnormal ECG finding as SFSR-positive
Only new ECG changes, non-sinus rhythm, or pacemaker malfunction count. Chronic stable abnormalities without change should not be counted.
Using SFSR to rule out non-syncope causes of collapse
SFSR predicts serious outcomes in syncope patients. It does not diagnose the cause of syncope and does not replace clinical judgment for specific etiologies like PE or MI.
Frequently Asked Questions
Does a negative SFSR mean I can always discharge the patient from the ED?
What defines an abnormal ECG in SFSR?
Can SFSR be used in pediatric syncope?
References
- Quinn JV, Stiell IG, McDermott DA, et al. Derivation of the San Francisco Syncope Rule to predict patients with short-term serious outcomes. Ann Emerg Med. 2004;43(2):224-232. PubMed
- Quinn JV, McDermott DA, Stiell IG, et al. Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes. Ann Emerg Med. 2006;47(5):448-454. PubMed
- American College of Emergency Physicians. Clinical policy: critical issues in the evaluation and management of adult patients presenting to the emergency department with syncope. Ann Emerg Med. 2017;49(4):437-444.