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Validating the San Francisco Syncope Rule
Abstract & Commentary
By John Shufeldt, MD, JD, MBA, FACEP, Chief Executive Officer, NextCare, Inc.; Attending Physician/Vice Chair, Department of Emergency Medicine, St. Joseph's Hospital and Medical Center, Mesa, AZ, is Editor for Urgent Care Alert.
Dr. Shufeldt reports no financial relationship to this field of study.
Synopsis: The San Francisco Syncope Rules is used to identify patients presenting to the ED with a low risk of adverse outcome in the succeeding sever days. This study attempts to externally validate the rules.
Source: Sun BC, et al. External validation of the San Francisco Syncope Rule. Ann Emerg Med. 2007;49:420-427.
The object of this original study was to determine
if the San Francisco Syncope Rule can be externally validated. The San Francisco syncope rule was developed to try to stratify which patients are at low risk for an adverse event within the succeeding 7 days. In the initial study, the Rule was determined to be 96% to 98% sensitive.
Syncope is defined as a transient loss of consciousness, and may be the first sign of a life-threatening event. Syncope accounts for 1-3% of all emergency department visits and admissions to the hospital. Approximately 39-50% of all patients admitted with syncope leave without a definitive diagnosis.
The San Francisco Syncope Rule predictors include an abnormal EKG, complaint of shortness of breath, a hematocrit level less than 30%, a systolic blood pressure less than 90 mm Hg, and a history of congestive heart failure. Of note, age was not a predictor.
In this study, both the primary outcome included all 7-day serious events and the secondary outcome included all 7-day outcomes that were diagnosed only after the original ED visit. Of the 709 patients who were screened initially, 477 were eventually enrolled in the study. The proportion of patients with a serious 7-day event was 11.7%. The proportion of patients who had a serious event diagnosed only after admission was 3.4%. These serious events included: arrhythmia, hemorrhage/anemia, structural heart disease, stroke/TIA, pacemaker placement, PTCA, MI, PE, ICH, and aortic dissection.
Out of the 477 patients who provided informed consent, telephone follow-up was completed in 463. There were 56 (12%) patients who had a serious 7-day clinical event, including 16 (3%) who received a diagnosis after the initial ED evaluation. The sensitivity of the San Francisco Syncope Rule for the primary outcome was 89% (95% confidence interval 37% to 48%). The specificity for the primary outcome was 42% (95% confidence interval 81% to 97%). For the secondary outcome (diagnosis after ED visit), sensitivity was 69% (95% confidence interval 46% to 92%) and specificity was 42% (95% confidence interval 37% to 48%)
This study used the San Francisco Syncope Rule to predict serious events within 7 days of the initial event. Sun and colleagues determined that the Rule had a lower sensitivity and specificity than was previously reported.
This study is useful to those of us in urgent care centers who struggle with the disposition for patients with the diagnosis of syncope. Syncope is a frequent presenting complaint in urgent care centers. If your center has ECG and hematocrit available, you may be able to manage those patients presenting with syncope, provided that the patient does not have an abnormal EKG, complaint of shortness of breath, a hematocrit level less than 30%, a systolic blood pressure less than 90 mm Hg, and a history of congestive heart failure.
If you elect to manage them on an outpatient basis as opposed to sending them to the emergency department, you have some data to support you. Recall that age was not a variable which Sun et al used and will obviously weigh into your decision process. Also recall that Sun et al were only looking in a 7-day window. In other words, try to determine which patients may benefit from hospitalization. One important caveat is that if you send the patient home who meets criteria, ensure that they have adequate follow-up to complete their syncope work up.