Thirty-Day Versus 7-Day Outcomes in the San Francisco Syncope Rule
Article Outline
To the Editor:
We read with interest the validation study of the San Francisco Syncope Rule by Quinn et al1 in the May 2006 issue of Annals of Emergency Medicine. The authors concluded that the San Francisco Syncope Rule performed with high sensitivity and specificity and therefore recommended its use as a risk stratification tool for patients who present to the emergency department with syncope.
We have one main concern regarding the validation study. Why did the authors use 30-day outcomes instead of 7-day outcomes since the authors used 7-day outcomes in the derivation study?2 The authors cited no fewer than 5 times in the derivation study the relevance and clinical importance of 7-day outcomes on the disposition decision for patients with syncope. They specifically mentioned that 30-day outcomes for risk stratifying patients for inpatient admission may not be as clinically useful. Therefore to assess the true value of the San Francisco Syncope Rule, it would be useful if the authors could report the results of the 7-day outcomes to match the derivation study. The power calculation for the validation study described needing approximately 50 outcomes to validate the rule for 7-day outcomes. We deduced that many of the outcomes probably occurred on days 8 to 30 and the authors decided to use 30-day outcomes instead of 7-day outcomes during the data analysis and manuscript preparation phase. The effect of using a 7-day outcome in the validation study likely would not have changed the point estimate for the sensitivity appreciably but probably would have widened the confidence interval. In addition, the reported specificity using a 30-day outcome is likely an overestimate of the true specificity for the clinically relevant 7-day outcome. These considerations may minimize the impact of the San Francisco Syncope Rule on clinical practice.
Armed with this additional information, clinicians in emergency medicine practice may have a better idea about whether or not to use the San Francisco Syncope Rule to augment admission decisions for patients with syncope.
References
PII: S0196-0644(06)02249-9
doi:10.1016/j.annemergmed.2006.06.055
© 2006 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.
