Characteristics of Patients.

Pneumonia was defined as evidence of clinical signs and symptoms of pneumonia and evidence of infiltrate in CTPA that was not attributable to pulmonary infarction due to PE, and a final diagnosis of pneumonia before leaving the ED. An acute cardiac disorder was defined as the diagnosis of acute coronary syndrome, confirmed by coronary angiography (ACS), acute left ventricular failure or cardiogenic shock, or tachyarrhythmia before leaving the ED. All patients who failed to meet the criteria of pneumonia or acute cardiac disorder were allocated to the comparison group. IQR denotes interquartile range. CPR denotes cardiopulmonary resuscitation.*Pneumonia group vs. comparison group;†acute cardiac disorder group vs. comparison group;‡pain or swelling of a limb;§≥100 beats/minute;||history of surgery during previous month;¶history of hospitalization during previous month;**CTPAs that was ordered to evaluate the patient for PE only and not for an additional disease such as consequences of trauma, suspected pulmonary disease, cancer or aortic dissection;††estimated by using simplified revised Geneva score (see Table S1);‡‡