OBJECTIVES: Patients with panic-related anxiety frequently seek care in the Emergency Department (ED), but panic-related anxiety is rarely diagnosed by ED physicians due to limited time and a focus on stabilizing life-threatening conditions. We have previously developed a brief clinical decision rule (CDR) to help physicians quickly identify patients with panic-related anxiety in the ED setting. This study was undertaken to cross-validate the original CDR with a larger group of patients. METHODS: English and Mandarin-speaking adult ED patients with a primary complaint of palpitations, chest pain, dizziness, or difficulty breathing were evaluated for the presence of panic-related anxiety (i.e., panic attacks or panic disorder) using the Structured Clinical Interview for DSM-IV. All 13 panic attack symptoms were entered into a multivariate model using stepwise selection with presence/absence of panic-related anxiety as the outcome variable. We compared receiver operating characteristics, sensitivity, and specificity for the original 7-item CDR created with our derivation sample (n=200) versus an alternative 7-item CDR created with the validation sample (n=321) using the same model selection procedure. RESULTS: