Failure to Externally Validate the San Francisco Syncope Rule
Search Strategy: Using the combined search terms of “syncope AND Emergency Department” you conduct a PUBMED query which yields 319 hits. Scrolling down the list the article by Adrienne Birnbaum, MD – Failure to Validate the San Francisco Syncope Rule in an Independent Emergency Department Population catches your eye. Clicking on “related articles” then yields another 110 hits. In order to narrow the search, a second search is conducted using “San Francisco Syncope Rule” which yields 14 hits, of which four very relevent articles are found including the one above.
Ms. Jones is a 65 year old African American female with a history of HTN and type II DM who presents to the E.D. after a syncopal event which occurred 30 minutes prior to arrival. The event was witnessed by the patient’s husband who states she had collapsed soon after getting up from her recliner to go to the restroom. He notes that she fell against the wall and landed on her buttocks. She did not hit her head and had no seizure activity. The patient regained consciousness within seconds returning to a normal mental status. The patient does not remember the event and denies any precipitating symptoms, particularly no chest pain, shortness of breath, palpitations, headache, dizziness or vision changes. She denies any recent illness and her ROS is negative. She denies any hx of CAD, CHF or CVA/TIA. She is on Toprol XL and glyburide.
On exam the patient is awake, alert and oriented x 3. She is afebrile with a BP of 145/89, HR 68, RR 14 and a SaO2 of 98% on room air. Her d-stick is 122. The remainder of her physical exam is normal. Her ECG and labs are unremarkable including a Hct of 38%, a negative D-dimer, and initial troponin.
Using the San Francisco Syncope Rule (SFSR) you decide that the patient is at a low risk for serious outcome in the next 7 days and decide to discharge the patient with primary care physician follow-up within the next week. About an hour later your medicine colleague comes down to the E.D. to inquire about the patient who turns out to be his neighbor. When told she was discharged from the E.D. he asks you about the SFSR stating “Have any studies validated that this rule is safe and effective to use in our population?” Knowing that any questions raised by your medicine colleagues are solely for improvement in patient care, you turn to the medical literature.
Population: ED Syncope patients
Intervention: Use of risk stratification tools to identify high-risk syncope patients
Comparison: Unaided clinical intuition (physician gestalt)
Outcomes: Serious adverse outcome within 7 days (death, MI, PE, arrhythmia, CVA, significant hemorrhage, or any condition causing a return ED visit with hospitalization for a related event.
Article 1: Prospective Validation of the San Francisco Syncope Rule to Predict Patients With Serious Outcomes, Annals of Emergency Medicine 2006; 47: 448-454
Article 2: Failure to Validate the San Francisco Syncope Rule in an Independent Emergency Department Population, Annals of EM 2008
Article 3: External Validation of the San Francisco Syncope Rule Annals of Emergency Medicine 2007; 49:420-427
Article 4: External validation of the San Francisco Syncope Rule in the Australian context, CJEM 2007; 9: 157-161
In San Francisco, the SFSR has been validated to identify a low-risk subset of syncope or near-syncope ED patients for arrhythmia or MI (LR- = 0.03, 95% CI 0-0.2) reducing the post-test probability from 6.8% to 0.2% (95% CI 0-1.4%). Unfortunately, the SFSR did not validate in New York City or Australia and should not be used outside of San Francisco. Potential reasons why the rule failed to validate in one-setting versus another (http://pmid.us/14747813) include model instability, variable disease prevalence, or differences in application of the rule.