Neurology/original research
External Validation of the San Francisco Syncope Rule in the Canadian Setting

https://doi.org/10.1016/j.annemergmed.2009.10.001Get rights and content

Study objective

Syncope is a common disposition challenge for emergency physicians. Among the risk-stratification instruments available, only the San Francisco Syncope Rule is rigorously developed. We evaluate its performance in Canadian emergency department (ED) syncope patients.

Methods

This retrospective review included patients aged 16 years or older who fulfilled the definition of syncope (transient loss of consciousness with complete recovery) and presented to a tertiary care ED during an 18-month period. We excluded patients with ongoing altered mental status, alcohol/illicit drug use, seizure, and head and severe trauma. Patient characteristics, 5 predictors for the rule (history of congestive heart failure, hematocrit level <30%, abnormal ECG characteristics, shortness of breath, and triage systolic blood pressure <90 mm Hg), and outcomes (as per the original study) were extracted.

Results

Of 915 visits screened, 505 were included. Forty-nine (9.7%) visits were associated with serious outcomes. The rule performed with a sensitivity of 90% (44/49 outcomes; 95% confidence interval [CI] 79% to 96%) and a specificity of 33% (95% CI 32% to 34%). Including monitor abnormalities in the ECG variable would improve sensitivity to 96% (47/49 outcomes; 95% CI 87% to 99%). Although physicians failed to predict 2 deaths, the rule would have predicted all 3 deaths that occurred after ED discharge. Implementing the rule in our setting would increase the admission rate from 12.3% to 69.5%.

Conclusion

In this retrospective Canadian study, the San Francisco Syncope Rule performed with comparable sensitivity but significantly poorer specificity than previously reported. Implementing the rule would significantly increase admission rates. Further studies to either refine the San Francisco Syncope Rule or develop a new rule are needed.

Introduction

Syncope, defined as sudden transient loss of consciousness, followed by prompt, complete recovery, is a common presenting symptom to the emergency department (ED) and accounts for 1% to 3% of all ED visits and 2% of hospital admissions from the ED.1, 2, 3, 4, 5 Data from the National Hospital Ambulatory Medical Care Survey estimated 6.7 million syncope visits to US EDs from 1992 to 2000, with total cost of syncope-related hospitalization at $2.4 billion annually.3 ED evaluation of syncope patients is problematic because patients are often asymptomatic on arrival and the differential diagnosis ranges from benign to life-threatening causes.6 A survey among North American physicians identified syncope as the second most common decisionmaking problem.7 The evaluation, investigations ordered, and admission rates are highly variable among emergency physicians, institutions, and countries.8, 9, 10, 11, 12, 13 Although hospital admission provides only modest diagnostic and therapeutic benefit, most patients are admitted because of concern about potentially life-threatening sequelae, leading to high costs and inefficient use of resources.

Among the risk-stratification instruments available in the literature for predicting serious outcomes in ED syncope patients, the San Francisco Syncope Rule is the only one that includes all short-term serious outcomes and was prospectively derived and validated according to the methodological standards for clinical prediction rules.4, 5, 14, 15, 16, 17, 18 The San Francisco Syncope Rule had a sensitivity of 96% and specificity of 62% during the derivation phase for 7-day outcomes and sensitivity of 98% and specificity of 56% during the validation phase for 30-day outcomes. Investigators estimated that applying the rule to clinical practice had the potential to decrease admission rates by 7% to 10%.4, 5, 19 When the San Francisco Syncope Rule was validated in other US centers, it did not perform as well as previously reported.20, 21

The primary goal of this study was to externally validate the ability of the San Francisco Syncope rule to both diagnose and predict serious outcomes (ie, those occurring in the ED and after ED discharge) in Canadian ED syncope patients. Secondary goals were to assess the potential influence of implementation of the rule on the admission rate because it varies in Canada due to a public health payer system compared with that in the United States.

Section snippets

Study Design and Setting

This was a single-center health records review of consecutive adult patient visits to the ED for syncope. The study was conducted at the Ottawa Hospital Civic Campus ED, an urban adult tertiary care ED staffed by certified emergency physicians and with 60,000 annual patient visits. We reviewed charts of all eligible patients during an 18-month period from August 1, 2005, to January 30, 2007. The hospital research ethics board approved the protocol, without the need for informed consent.

Selection of Participants

We

Characteristics of Study Subjects

Of 915 potentially eligible patient visits screened, 530 (57.9%) met all inclusion criteria, with no exclusion criteria (Figure 2). Twenty-five visits (2.7%) could not be included; 13 subjects left the ED before assessment by the emergency physician and 12 records of treatment could not be located. As a result, 505 patient visits (55.2%) by 490 patients were included in the study.

The demographics, medical history, medications taken, investigations conducted, and disposition of the patients

Limitations

Many of the limitations of our study are typical of health records reviews. Although excluding patients without a local address and patients with presyncope may have introduced a degree of selection bias, we did this to ensure the fidelity of patient follow-up and avoid contamination by nonsyncope patients. Important clinical information may not have been elicited or recorded by the medical personnel delivering care, and the information in the patient's chart may have been misinterpreted by the

Discussion

To our knowledge, this is the first study to evaluate the performance of the San Francisco Syncope Rule in the Canadian setting. This is the largest study to validate the San Francisco Syncope Rule outside the United States and the second largest of all validation studies. We included consecutive eligible patients, thoroughly evaluated all records of treatment, and took extra steps to review records from all local hospitals and the provincial coroner's office to maximize the fidelity of patient

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    • Cited by (0)

    Supervising editor: Allan B. Wolfson, MD

    Author contributions: VT conceived the idea for the study, applied for funding, and wrote the article. VT, GAW, and IGS analyzed the data. EPH, AA, and IGS contributed to the acquisition and interpretation of the data. EPH, AA, and JJP were involved in drafting the article. EPH, AA, JJP, GAW, and IGS revised the article for important content. JJP, GAW, and IGS contributed to the design of the study. IGS supervised the conduct of the study. VT takes responsibility for the paper as a whole.

    Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article that might create any potential conflict of interest. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement. This study was funded by a grant from the Department of Emergency Medicine, University of Ottawa. The authors declare no potential conflicts of interest.

    Publication date: Available online November 27, 2009.

    Reprints not available from the authors.

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