San Francisco Syncope Rule

Predicts the risk of a serious life threatening outcome in patients suffering from syncope.

In the text below the calculator there is more information on the original study and on syncope symptoms and underlying conditions.

The San Francisco Syncope Rule is made out of 5 criteria which evaluates the risk, for the patient presenting with syncope in ER, to be suffering from a serious life threatening condition.

The criteria upon which SFSR is based is known under the CHESS mnemonic.

The SFSR helps reduce unnecessary hospital admissions upon triage of syncope patients in emergency rooms.

The rule is considered positive when either of the five criteria is present. 10% of SFSR positive patients and only 1.4% of SFSR negative patients exhibit an adverse outcome within 7 days from evaluation.

In a study of 791 syncope patients, 52% of them were classified as high risk and the rule was found to show 98% sensitivity and 56% specificity in predicting adverse outcomes.


History of congestive heart failure


Hematocrit below 30%


Abnormal EKG findings


Shortness of breath present


Systolic blood pressure below 90 mmHg

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The syncope rule

The San Francisco Syncope Rule predicts the risk of negative outcome in patients suffering syncope symptoms. The evaluation can take place in ER during a syncopal episode or outside of it.

The five criteria in the rule are known under the CHESS mnemonic:

■ Congestive heart failure history;

■ Hematocrit percentage below 30%;

■ ECG abnormal findings;

■ Shortness of breath;

■ Systolic blood pressure in triage less than 90 mmHg.

When either of the above is present, the patient is at risk of adverse outcome. When no criteria is present, the patient is not under risk.

Around 10% of SFSR positive patients (and around 1.4% of SFSR negative patients) return within 7 days from evaluation with signs of a more serious condition.

Some examples of possible life threatening conditions include:

■ Myocardial infarction;

■ Arrhythmia;

■ Pulmonary embolism;

■ Stroke;

■ Subarachnoid haemorrhage;

■ Significant hemorrhage.

The SFSR helps clinicians make the triage process more efficient when dealing with syncope presentation and helps reduce unnecessary admissions in patients who are not under risk of adverse outcomes and are suitable for outpatient monitoring.


About the study

The prediction rule was created by Quinn et al. in 2006, following a study on 791 consecutive patients with syncope or near syncope presentation to an emergency department.

For each case, the San Francisco Syncope Rule was applied during the ER evaluation and the patient status was followed up 30 days after emergency visit.

The study excluded patients with trauma, definite seizures and alcohol or drug induced loss of consciousness.

The rule has shown 98% sensitivity and 56% specificity in predicting adverse outcomes. 52% of patients were classified as high risk.

One validation study conducted by Birnbaum et al. found that the sensitivity and negative likelihood ratio of the San Francisco Syncope Rule were substantially lower than reported initially, therefore, suggesting that the rule only has limited generalizability.

James Quinn, MD is a Professor of Emergency Medicine at the Stanford University Medical Center and has researched extensively in the field of emergency medicine.


Syncope explained

Almost 2% of ER presentations include syncope, in most cases, without any underlying condition, however, in some cases, syncope might indicate the presence of a life-threatening disease.

Syncope is defined as a sudden, transient loss of consciousness with the inability to maintain postural tone.

Around 50% of syncope presentation cases are admitted. It was found that in around 85% of cases of hospitalized patients, admission is taken as a precaution rather than as necessity.

Syncope symptoms include:

■ Light-headedness;

■ Nausea;

■ Clammy skin.

The first action to be undertaken is to position the patient with legs elevated for several minutes to allow the return of blood to the brain.

Secondly, diagnosis of the underlying disease takes place in order to prevent other syncopal episodes from happening.

Arrhythmia is one of the most common underlying pathology found in patients with syncope. This can manifest through documented sinus pauses, severe bradycardia, and ventricular tachycardia. Left untreated, arrhythmias pose a major mortality risk.


Original source

Quinn J, McDermott D, Stiell I, Kohn M, Wells G. Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes. Ann Emerg Med. 2006; 47(5):448-54.

Other references

1. Birnbaum A, Esses D, Bijur P, Wollowitz A, Gallagher EJ. Failure to validate the San Francisco Syncope Rule in an independent emergency department population. Ann Emerg Med. 2008; 52(2):151-9.

2. Miller CD, Hoekstra JW. Prospective validation of the San Francisco Syncope Rule: will it change practice? Ann Emerg Med. 2006; 47(5):455-6.

3. Saccilotto RT, Nickel CH, Bucher HC, Steyerberg EW, Bingisser R, Koller MT. San Francisco Syncope Rule to predict short-term serious outcomes: a systematic review. CMAJ. 2011; 183(15):E1116-26.

Specialty: Cardiology

System: Cardiovascular

Objective: Risk Predictor

Type: Rule

No. Of Criteria: 5

Year Of Study: 2006

Article By: Denise Nedea

Published On: April 18, 2017

Last Checked: April 18, 2017

Next Review: April 18, 2023