Duration of Risk of Venous Thromboembolism in Real‐World U.S. Patients Hospitalized for Medical Illness

Background:

Patients hospitalized for medical illness are at an increased risk of developing venous thromboembolism (VTE). The present study retrospectively assessed the incidence and time course of symptomatic VTE events following hospitalization in a large, real‐world patient population.

Methods:

Administrative claims data derived from the Thomson Reuters MarketScan® Inpatient Drug Link File were used to identify patients hospitalized for severe infectious disease, congestive heart failure, cancer, or chronic obstructive pulmonary disease. Included patients had been admitted to the hospital between January 1, 2005, and December 31, 2008, and had been continuously enrolled ≥ 12 months prior to admission (patient history) and ≥ 180 days after admission. The cumulative risk and hazard of VTE—measured as the number of VTE events per 1000 person‐days—were established across an evaluation period of 180 days.

Results:

The study cohort consisted of 11,139 medical patients, with a mean (standard deviation [SD]) age of 67.6 (13.9) years, and 51.6% were female. The mean (SD) length of stay in the hospital was 5.3 (5.3) days, during which 46.7% of patients (ranging from 30.7% of cancer patients to 64.1% of heart failure patients) received any VTE prophylaxis for a mean (SD) duration of 5.0 (4.7) days. Enoxaparin was the most common prophylactic method (26.8%), 12.2% of patients received mechanical prophylaxis, and 8.8% of patients received anticoagulation therapy within the period extending from discharge to 35 days after discharge, most commonly with warfarin(7.7%). Appropriateness of prophylaxis was not determined. During the 180‐day evaluation period, 366 symptomatic VTE events occurred (3.3%), comprising 241 deep vein thrombosis (DVT)‐only events, 98 PE‐only events, and 27 events with evidence of both DVT and PE. Of the events, 43% (97 DVT only, 44 PE only, and 18 both DVT and PE) occurred during the index hospitalization. The highest number of VTE events occurred during the first 9 days (97 events, 88% in‐hospital; proportion of 180‐day cumulative risk, ∼20%) and during days 10‐–9 (82 events, 71% in‐hospital; proportion of 180‐day cumulative risk, ∼45%) following index admission. VTE hazard peaked at approximately 1.05 per 1000 person‐days on the eighth day following admission, and 50% had been incurred by the 23rd day. VTE frequency gradually declined thereafter, fluctuating at a background level of 4–7 events during each 10‐day interval from 130 to 139 days up to 170–180 days.

Conclusions:

Among the cohort of 11,139 medical patients at risk of VTE, 3.3% experienced a symptomatic VTE event during the 180‐day evaluation period following index hospitalization, and more than half of these events (57%) occurred postdischarge. Although the risk of VTE was highest within the first 19 days after the index admission, results from this study indicate that a considerable risk of VTE extends into the period after discharge.

Disclosures:

A. Amin ‐ sanofi‐aventis U.S., Inc., research honorarium, speakers bureau; H. Varker ‐ sanofi‐aventis U.S., Inc., employee at Thomson Reuters, which received funding to carry out this work from sanofi‐aventis U.S., Inc.; J. Lin ‐ sanofi‐aventis U.S., Inc., employee at Bruce Wong & Associates Inc., which received funding to carry out this work from sanofi‐aventis U.S., Inc.; S. Thompson ‐ sanofi‐aventis U.S., Inc., employment; S. Johnston ‐ sanofi‐aventis U.S., Inc., employee at Thomson Reuters, which received funding to carry out this work from sanofi‐aventis U.S., Inc