Summary. Backgound: Over-investigation of low-risk patients with suspected pulmonary embolism (PE) represents a growing problem. The combination of gestalt estimate of low suspicion for PE, together with the PE rule-out criteria [PERC()): age < 50 years, pulse < 100 beats min, SaO 2 ‡ 95%, no hemoptysis, no estrogen use, no surgery/trauma requiring hospitalization within 4 weeks, no prior venous thromboembolism (VTE), and no unilateral leg swelling], may reduce speculative testing for PE. We hypothesized that low suspicion and PERC()) would predict a post-test probability of VTE(+) or death below 2.0%. Methods: We enrolled outpatients with suspected PE in 13 emergency departments. Clinicians completed a 72-field, web-based data form at the time of test order. Low suspicion required a gestalt pretest probability estimate of <15%. The main outcome was the composite of image-proven VTE(+) or death from any cause within 45 days. Results: We enrolled 8138 patients, 85% of whom had a chief complaint of either dyspnea or chest pain. Clinicians reported a low suspicion for PE, together with PERC()), in 1666 patients (20%). At initial testing and within 45 days, 561 patients (6.9%, 95% confidence interval 6.5-7.6) were VTE(+), and 56 others died. Among the low suspicion and PERC()) patients, 15 were VTE(+) and one other patient died, yielding a false-negative rate of 16/1666 (1.0%, 0.6-1.6%). As a diagnostic test, low suspicion and PERC()) had a sensitivity of 97.4% (95.8-98.5%) and a specificity of 21.9% (21.0-22.9%). Conclusions:The combination of gestalt estimate of low suspicion for PE and PERC()) reduces the probability of VTE to below 2% in about 20% of outpatients with suspected PE.

Objectives Available D-dimer assays have low specificity and may increase radiographic testing for pulmonary embolism (PE). To help clinicians better target testing, this study sought to quantify the effect of risk factors for a positive quantitative D-dimer in patients evaluated for PE. Methods This was a prospective, multicenter, observational study. Emergency department (ED) patients evaluated for PE with a quantitative D-dimer were eligible for inclusion. The main outcome of interest was a positive D-dimer. Odds ratio (ORs) and 95% confidence intervals (CIs) were determined by multivariable logistic regression. Adjusted estimates of relative risk were also calculated. Results A total of 4,346 patients had D-dimer testing, of whom 2,930 (67%) were women. A total of 2,500 (57%) were white, 1,474 (34%) were black or African American, 238 (6%) were Hispanic, and 144 (3%) were of other race or ethnicity. The mean (±SD) age was 48 (±17) years. Overall, 1,903 (44%) D-dimers were positive. Model fit was adequate (c-statistic = 0.739, Hosmer and Lemeshow p-value = 0.13). Significant positive predictors of D-dimer positive included female sex; increasing age; black (vs. white) race; cocaine use; general, limb, or neurologic immobility; hemoptysis; hemodialysis; active malignancy; rheumatoid arthritis; lupus; sickle cell disease; prior venous thromboembolism (VTE; not under treatment); pregnancy and postpartum state; and abdominal, chest, orthopedic, or other surgery. Warfarin use was protective. In contrast, several variables known to be associated with PE were not associated with positive D-dimer results: body mass index (BMI), estrogen use, family history of PE, (inactive) malignancy, thrombophilia, trauma within 4 weeks, travel, and prior VTE (under treatment). Conclusions Many factors are associated with a positive D-dimer test. The effect of these factors on the usefulness of the test should be considered prior to ordering a D-dimer.

I ABSTRACTObjective: To determine whether the shock index (SI), defined as the ratio of heart rate (HR) to systolic blood pressure (SBP), is a useful marker for significant injury in trauma patients. Methods: A retrospective database analysis was used to relate the SI to the clinical measures: death within 24 hours, injury severity score (ISS) 2 16, intensive care unit (ICU) stay 2 1 day, and amount of blood transfused (BT) 2 2 units. Consecutive trauma patients seen at one level I trauma center over a 24-month period were reviewed; excluded were patients not requiring trauma team consultation, or those with either incomplete records, severe head injury (Glasgow Coma Scale score 18), or age <14 years. The SI was calculated from ED admission vital signs. Receiver operating characteristic (ROC) curves were used to find the value of the SI that maximized the sum of sensitivity and specificity for predicting each measure, separately; a separate analysis was done to determine the optimal SI threshold for predicting any of the severity measures. Results: 1,101 cases met study criteria. The optimal SI values (by ROC analysis) for predicting the severity measures were: 1.10 for death <24 hours, 0.71 for ISS 2 16, 0.77 for ICU Z 1 day, and 0.85 for BT 2 2 units. The optimal SI value (by ROC analysis) for any of the above measures was 0.83; use of this SI cutoff provided a sensitivity of 37% (95% CI 32-42%), a specificity of 83% (95% CI 80-87%). and a negative predictive value of 58% (95% CI 54-61%) for any measure. This SI threshold predicted between 24% fewer cases and 4% more cases of poor outcome than did the optimal thresholds HR and SBP, respectively. Conclusion: The optimal SI threshold performed similarly to the optimal threshold HR or SBP for prediction of injury severity2 Key words: blood pressure; heart rate; sensitivity and specificity; shock; shock index; trauma; triage; vital signs. Acad. Emerg. IThe emergency evaluation of trauma victims can be challenging when vital signs and physical examination findings do not reflect severe occult injuries. The use of the shock index (SI), defined as the ratio of heart rate (HR) to systolic blood pressure (SBP), has been suggested as a marker for shock, persistent decreased central venous oximetry, and lactic acidosis in patients in the ED setting. ' The SI has been correlated with the degree of shock, decreased tissue oxygenation, and left ventricular (LV) performance,2 and values >0.9 have identified ED patients requiring immediate therapy, admission, and intensive care unit (ICU) care.3 The utility of the SI in identifying the severely ill trauma victim remains unknown.The purpose of this study was to examine the SI as a