Background-Serial ultrasonography is reliable for the diagnosis of deep venous thrombosis in symptomatic patients, but the low prevalence of thrombosis in this group renders the approach costly and inconvenient to patients. We studied the clinical validity of the combination of a pretest clinical probability score and a D-dimer test in the initial evaluation of patients suspected of deep venous thrombosis. Methods and Results-Patients with a normal D-dimer concentration (Ͻ500 fibrin equivalent units [FEU] g/L) and a non-high probability score (Ͻ3) had no further testing. Patients with a normal D-dimer concentration and a high probability score (Ն3) underwent one ultrasonogram. Serial ultrasonography was performed in patients with an abnormal D-dimer concentration. Patients were followed for 3 months. A total of 812 patients were evaluable for efficacy. Only 1 of 176 patients (0.6%; 95% CI, 0.02% to 3.1%) with a normal D-dimer concentration and a non-high probability score developed thrombosis during follow-up. A normal D-dimer concentration and a high probability score were found in 39 patients; 3 of them (7.7%; 95% CI, 1.6% to 20.9%) had thrombosis at presentation, and one (2.8%; 95% CI, 0.07% to 14. 5%) developed pulmonary embolism during follow-up. In 306 of 597 patients (51.3%) with an abnormal D-dimer concentration, thrombosis was detected by serial ultrasonography. Six patients (2.1%; 95% CI, 0.8% to 4. 4%) developed thrombosis during follow-up. No deaths due to thromboembolism occurred during follow-up. The total need for ultrasonography was reduced by 29%. Conclusion-The combination of a non-high pretest clinical probability score and a normal D-dimer concentration is a safe strategy to rule out deep venous thrombosis and to withhold anticoagulation. (Circulation. 2003;107:593-597.)

http://clinicaltrials.gov/ct2/show/NCT00455819.

Outpatient treatment of patients with PE selected on the basis of the Hestia criteria alone was associated with a low risk of adverse events. Given the low number of patients with elevated NT-proBNP levels, this trial was unable to draw definite conclusions regarding the incremental value of NT-proBNP testing in patients who fulfill the Hestia criteria. Clinical trial registered with www.trialregister.nl/trialreg/admin/rctview.asp?TC=2603 (NTR2603).

3996 Poster Board III-932 Background NT-proBNP is emerging to be of great importance in risk assessment of patients with acute pulmonary embolism (PE), by identifying both high and low-risk patients. The aim of the present management study was to investigate the safety of out of hospital treatment of patients with acute PE based on a NT-proBNP < 500 pg/ml. Methods Hemodynamically stable outpatients with objectively diagnosed acute PE and a NT-proBNP level < 500 pg/ml, were considered eligible for participation in this multicenter prospective study. Patients were discharged immediately from the emergency room or within the first 24 hours of admission. The primary objective was the 10-days mortality rate. Secondary objectives were the incidence of re-admission to hospital due to PE or its treatment, the patient's satisfaction during the first ten days of treatment and the incidence of serious adverse events in a 3-month follow-up period. Results Approximately 40 percent of all patients presenting at the emergency room with acute PE fulfilled the inclusion criteria. In total, 152 patients (mean age 53.4 ± 14.3 years; 51% female) with PE were treated as outpatients. No deaths, major bleedings or recurrent venous thromboembolism occurred during the first 10 days or in a follow-up period of 3 months. Seven patients required readmission. Three patients were admitted because of complaints of their PE: two patients with anxiety and pain and one patient with dyspnoea and low oxygen saturation. There were no signs of progression of PE in these 3 patients. Four patients were re-admitted because of an illness unrelated to PE. According to the PSQ18 and anxiety score, patients were satisfied with their out of hospital treatment; they had no progression of anxiety during the first ten days of treatment. Conclusion Out of hospital treatment is safe in a group of low risk patients with non-massive PE, based on NT-proBNP levels < 500 pg/ml. Approximately 40 percent of PE-patients can be treated in an outpatient setting. Patients consider out of hospital treatment as comfortable and have no increase in anxiety scores. Disclosures: No relevant conflicts of interest to declare.

Pathological elevations of the plasma activities of liver enzymes are not simply related to the quantitative release of such enzymes from the liver. Several enzymatic indices, such as the well-known de Ritis quotient, may be determined by differences in the time course of hepatic enzyme release, rather than reflecting true differences in the released quantities of various enzymes. A more quantitative use of enzymatic data is hampered by the fact that the fractional catabolic rate constants for the elimination of enzyme activities from plasma are unknown. In the present study, three of these constants are estimated by comparison of the time-activity curves in plasma with the corresponding curve of a simultaneously released, more slowly eliminated reference enzyme. This method can be applied in patients with an acute short period of hepatic enzyme release. Values obtained for the cytosolic isoforms of lactate dehydrogenase, AST and ALT are: fractional catabolic rate constant (lactate dehydrogenase isoenzyme 5) = 0.13 +/- 0.01 hr-1, fractional catabolic rate constant (cytosolic AST) = 0.088 +/- 0.016 hr-1 and fractional catabolic rate constant (cytosolic ALT) = 0.034 +/- 0.004 hr-1 (mean +/- S.E., n = 10). These values are much higher than the apparent disappearance rate constants, because of extravascular return of activity and tailing release of enzymes during the major part of the elimination phase. It is shown that these results are consistent with earlier published data on the disappearance rates from plasma of lactate dehydrogenase, AST and ALT after acute liver injury. Cumulative release of various cytosolic enzymes occurred in proportion to the corresponding activities in human control livers.