Study of Blood Clots in a Racially Diverse Population Finds Differences in the Rate of New Cases and Deaths by Race


Diverse group of co-workers standing outside their office.

Venous thromboembolism (VTE), also known as blood clots, is an important public health problem. The precise number of people affected by VTE in the United States is uncertain, but researchers estimate that for every 1,000 Americans, 1–2 people will develop a blood clot each year.  In addition, researchers believe that VTE is responsible for about 60,000–100,000 deaths each year and is associated with about $10 billion in yearly healthcare costs.

Previous information from studies of people from various populations in the United States is outdated and limited to studies among mostly white people.  Current information on the number of people with VTE in the United States is needed because population demographics, such as age, race, or ethnicity, and factors that might increase a person’s risk for VTE, such as being overweight or obese, change over time.  In this study, researchers assessed VTE among a racially diverse group of people living in Oklahoma County, Oklahoma.

About This Study

Researchers from the University of Oklahoma Health Services Center, along with the Centers for Disease Control and Prevention, conducted VTE surveillance (collecting or gathering of health information) in Oklahoma County from April 1, 2012 to March 31, 2014, using several methods (how the study was done or carried out).

  • They actively sought to identify new VTE events (occurrence of VTE) by working with hospitals and outpatient clinics that perform imaging tests to diagnose VTE.
  • They identified past VTE events by reviewing hospital discharge and death certificate records.
  • They linked information collected from all sources to make sure each VTE event for a given person was counted only once.

Main Findings of This Study

A total of 3,815 VTE events were identified among 3,422 unique patients over the study period.  Below are the main findings:

  • Out of every 1,000 people in Oklahoma County, OK, there were 2.26 new cases of VTE overall and 3.02 new cases among adults.
    • The rate of new cases of VTE increased with each decade (a period of 10 years of age), reaching 13.16 among those 80 years of age or older.
    • The rate of new cases of VTE varied greatly by race. It was highest among Non-Hispanic Blacks (3.25), followed by Non-Hispanic Whites (2.71), Native Americans (1.25), Hispanics (0.67), and Asians/Pacific Islanders (0.63).
    • Over one-third (36.2%) of the VTEs were among people who were currently hospitalized or had recently been hospitalized (referred to as hospital-associated VTE).
  • Hospital-associated VTE is often preventable with medications or leg compression devices (these types of preventive measures are referred to as VTE prophylaxis). In this study, 84.8% of patients were not receiving some type of VTE prophylaxis at the time of their VTE.
  • About 1 in 10 (9.5%) patients had more than one VTE event during the 2-year surveillance period.
  • The overall rate of death within 30 days of being diagnosed with a VTE was 0.34 per 1,000 people. Among adults, the death rate was 0.41 per 1,000 adults.
    • The death rate increased with each decade of age, reaching 3.07 among those 80 years of age or older.
    • The death rate varied with race. Deaths were highest among Non-Hispanic Whites (0.40), followed by Non-Hispanic Blacks (0.36), Native Americans (0.20), Asians/Pacific Islanders (0.12), and Hispanics (0.11).

Future Directions

The rate of new cases of VTE reported each year in this study is higher than previously reported in other U.S. populations.  Many VTE events are still linked to hospitalization.  Despite the toll VTE takes on health, there is no VTE surveillance system in the United States that can systematically collect nationally representative data on VTE rates, complications, and deaths.  CDC is exploring how VTE surveillance activities might be expanded in the United States.


Wendelboe AM, Campbell J, Ding, K, Bratzler DW, Beckman MG, Reyes NL, Raskob GE.  Incidence of venous thromboembolism in a racially diverse population of Oklahoma County, Oklahoma. Thrombosis and Haemostasis. 2021 Jan. doi: 10.1055/s-0040-1722189. Online ahead of print.