Traditional therapy for deep venous thrombosis (DVT) has been unfractionated intravenous heparin. Studies over the past five years have shown that subcutaneously administered low-molecular-weight heparin (LMWH) is also a safe and effective therapy. Advantages to LMWH include ease of administration and infrequent monitoring of partial thromboplastin time. These findings have prompted additional studies evaluating the efficacy of LMWH in treating DVT in the outpatient setting. Yusen and colleagues developed specific selection criteria for patients with proximal DVT who could be treated safely in an outpatient setting.

Patients who underwent lower extremity duplex ultrasound testing during a one-year period were eligible for the study. The medical records of patients who were hospitalized with ultrasound results positive for DVT were evaluated further. Even though all patients were ultimately admitted, the timing of the Doppler study in relationship to hospitalization was used to classify the presentation as an inpatient or outpatient event. For a list of exclusion criteria designed to identify patients at risk for complications from anticoagulation, see the accompanying table.

Once established, the exclusion criteria were applied retrospectively to all patients who met the initial study criteria. Patients were then classified as eligible, possibly eligible or ineligible for outpatient therapy. Complications that developed during hospitalization were recorded, including major bleeding, recurrent symptomatic thromboembolic event and death.

A total of 1,200 Doppler studies were performed and 203 (17 percent) were positive for proximal lower extremity DVT. A total of 195 records were analyzed for the study. Approximately 30 percent of patients were diagnosed on an outpatient basis, and 70 percent were already hospitalized. After application of all exclusion criteria, 18 percent of patients were classified as eligible or possibly eligible for outpatient anticoagulation therapy. None of these patients experienced any of the major complications noted above. A total of 159 patients were considered ineligible for outpatient therapy. Of these, 10 died, one had non-fatal bleeding, and two had a nonfatal symptomatic pulmonary embolism. The sensitivity of the exclusion criteria was 100 percent in patients considered eligible or possibly eligible for outpatient therapy, and the negative predictive value was 100 percent for predicting serious complications. Age 75 was the lower age limit for the ineligible group, as the frequency of complications in patients older than this was significantly higher.

The authors conclude that applying strict exclusion criteria to patients with proximal DVT makes outpatient anticoagulation therapy a reality for a certain subset of patients. The percentage of patients (up to 18 percent) in this study reported eligible or possibly eligible is actually lower than that reported in other studies. The current study did not include patients with distal lower extremity DVT, which might explain the difference in results. Patients considered for outpatient treatment are younger than 75 years of age, do not require hospitalization for other conditions, are not at high risk for bleeding or recurrent clot formation, have no symptoms of pulmonary embolism and have adequate cardiopulmonary reserve should a major hemorrhage or recurrent DVT occur.

editor's note: With the recent U.S. Food and Drug Administration labeling of LMWH for the outpatient treatment of DVT, this type of management will become a growing trend. Studies such as this one should help physicians decide when hospital admission is necessary and when outpatient treatment is possible. Further validation of the criteria in this study through a prospective clinical trial is needed.—j.t.k.