Duration of venous thromboembolism risk across a continuum in medically ill hospitalized patients.

BACKGROUND: Patients hospitalized for medical illness are at increased risk of venous thromboembolism (VTE), but the duration of risk is not well understood.
OBJECTIVE: To assess incidence and time course of symptomatic VTE following hospitalization for medical illness in a large, real-world patient population.
DESIGN: Data were extracted from the Thomson Reuters MarketScan(®) Inpatient Drug Link File. PATIENTS: Those hospitalized with cancer, heart failure, severe lung disease, or infectious disease from 2005 to 2008. MEASUREMENTS: The cumulative VTE risk over 180 days after admission was calculated using Kaplan-Meier analysis. VTE hazard was calculated on a daily basis and smoothed through LOESS regression.
RESULTS: The analysis included 11,139 medically ill patients, 46.7% and 8.8% of whom received pharmacological thromboprophylaxis during hospitalization and after discharge, respectively. The mean duration of prophylaxis during hospitalization was 5.0 days. Of the 11,139 patients, 366 (3.3%) experienced a symptomatic VTE event. VTE events were most frequent during days 0-9 (97 events), followed by days 10-19 (82 events). The mean length of hospital stay was 5.3 days, and 56.6% of all VTE events occurred after discharge. VTE hazard peaked at day 8, with 1.05 events per 1000 person-days.
CONCLUSIONS: The time course of VTE in medical patients shows that risk of symptomatic VTE is highest during the first 19 days after hospital admission, and extends into the period after discharge. Future research is warranted to investigate risks and benefits of reducing the incidence of VTE after discharge, including the role of improving thromboprophylaxis practices in the inpatient setting and extending thromboprophylaxis after hospitalization.