San Francisco Syncope Rule to predict short-term serious outcomes: a systematic review

Abstract

Background: The San Francisco Syncope Rule has been proposed as a clinical decision rule for risk stratification of patients presenting to the emergency department with syncope. It has been validated across various populations and settings. We undertook a systematic review of its accuracy in predicting short-term serious outcomes.

Methods: We identified studies by means of systematic searches in seven electronic databases from inception to January 2011. We extracted study data in duplicate and used a bivariate random-effects model to assess the predictive accuracy and test characteristics.

Results: We included 12 studies with a total of 5316 patients, of whom 596 (11%) experienced a serious outcome. The prevalence of serious outcomes across the studies varied between 5% and 26%. The pooled estimate of sensitivity of the San Francisco Syncope Rule was 0.87 (95% confidence interval [CI] 0.79-0.93), and the pooled estimate of specificity was 0.52 (95% CI 0.43-0.62). There was substantial between-study heterogeneity (resulting in a 95% prediction interval for sensitivity of 0.55-0.98). The probability of a serious outcome given a negative score with the San Francisco Syncope Rule was 5% or lower, and the probability was 2% or lower when the rule was applied only to patients for whom no cause of syncope was identified after initial evaluation in the emergency department. The most common cause of false-negative classification for a serious outcome was cardiac arrhythmia.

Interpretation: The San Francisco Syncope Rule should be applied only for patients in whom no cause of syncope is evident after initial evaluation in the emergency department. Consideration of all available electrocardiograms, as well as arrhythmia monitoring, should be included in application of the San Francisco Syncope Rule. Between-study heterogeneity was likely due to inconsistent classification of arrhythmia.

Figure 1:

Identification of studies for a systematic review of the San Francisco Syncope Rule.

Figure 2:

Plot of true positive rate v. false positive rate for studies included in the systematic review of the San Francisco Syncope Rule (SFSR). The 95% confidence region shows the precision of the pooled estimates based on the random-effects model. The 95% prediction area illustrates the between-study variability (i.e., the range that contains 95% of all pairs of individual study test characteristics). The size of the plotted point for each study indicates its relative sample size.