Having an existing health condition and certain hospital characteristics are associated with chances of hospitalized patients being diagnosed with a blood clot

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Adults in the hospital with a pre-existing condition were about 3 times more likely to get a life-threatening blood clot.

Blood clots or venous thromboembolism (VTE) comprise both deep vein thrombosis (DVT) and pulmonary embolism (PE). Affecting up to 900,000 people each year in the United States and claiming up to 100,000 lives, VTE is a serious medical and public health concern. VTE is common among people who are hospitalized, but can be prevented by physicians who assess a patient’s risk for developing a blood clot and follow recommended practice guidelines. Learning the factors that may place a hospitalized patient at higher risk for developing a blood clot is important to inform future prevention efforts.

About this Study

CDC conducted a study among 6,710,066 hospitalizations of US adults from 1,039 hospitals to learn how a diagnosis of a DVT was related to

  • Patient characteristics, such as age, sex, and race or ethnicity, and whether or not a patient has health insurance or a pre-existing health condition; and
  • Hospital characteristics, such as bed size, ownership, location and teaching status.

This study, published in the Public Library of Science journal (PLoS ONE), used data from the Nationwide Inpatient Sample (NIS) developed through the Agency for Healthcare Research and Quality’s Healthcare Cost Utilization Project. In 2011, the rate of VTE diagnosis was 2.4% overall among hospitalizations of adults. The rate varied by age, sex, race or ethnicity, total days of hospital stay, primary expected payer of insurance, and whether there was an operating room procedure, such as surgery.

We invite you to read the study’s abstract or full text here.


What is Venous Thromboembolism (VTE)?
Venous thromboembolism includes both deep vein thrombosis (DVT) and pulmonary embolism (PE), and is an important and growing public health issue.

What is Deep Vein Thrombosis (DVT)?
Deep Vein Thrombosis is a condition in which blood clots form in the deep veins of the body, typically in the legs, although sometimes in the arms.

What is Pulmonary Embolism (PE)?
Pulmonary Embolism occurs when a clot in a deep vein breaks free and travels through the heart to block arteries of the lungs.

Main Findings from this Study

  • High rates of VTE diagnosis were observed among particular subgroups of hospitalized individuals: adults who were 80 years of age or older (3.0%), male (2.9%), Black (2.7%), had at least 7 total days of hospital stay (5.7%), had Medicare insurance as primary expected payer (2.9%), or had no operating room procedures of any kind (2.7%).
  • Hospitalized adults with preexisting health conditions were almost 3 times more likely to be diagnosed with VTE than hospitalized adults without any of these conditions.  The preexisting conditions included AIDS, anemia, arthritis, congestive heart failure, clotting disorders, high blood pressure, cancers, disorders of the brain, spinal cord or nerves, obesity, paralysis, disorders affecting blood flow in the lungs, kidney failure, and weight loss.
    • The presence of 2 or more of these conditions substantially increased the likelihood of a VTE diagnosis.
  • Hospitalized adults who were treated in urban hospitals were more likely to have a diagnosis of VTE than those treated in rural hospitals.
  • About 7% of the difference in the rate of VTE diagnosis between hospitals could be accounted for by differences in hospital characteristics, such as bed size, ownership, location and whether or not it was a teaching hospital.

Critical Gaps & Future Directions

Because the NIS did not identify how many times the same patient was hospitalized, patient-level analysis could not be performed. This study could not determine if a VTE event had been present on admission to the hospital or had occurred during a hospital stay. Some preexisting health conditions (such as obesity and weight loss) were not defined or measured in the same way from hospital to hospital. The differences in VTE diagnosis may have arisen from other factors such as availability and accessibility of advanced equipment and services that could not be evaluated in this study.  Despite these gaps and limitations, the study provided important information for healthcare providers and patients about VTE prevention:

Healthcare providers need to be informed of various factors that increase the risk for VTE among hospitalized patients so that they

  • Perform appropriate risk assessments to identify those patients who are at an increased risk of VTE, and
  • Provide counseling to those who might benefit from preventive treatment for VTE, such as use of blood thinners or compression stockings.

Patients should

  • Keep their doctors informed about their medical history and health conditions,
  • Discuss VTE prevention with their doctors during their hospital stay, and
  • Adhere to prescribed therapies.

The effects and complex nature of the factors that increase the risk for VTE suggest the need for public health approaches and evidence-based research to identify strategies targeting multiple audiences to prevent VTE among hospitalized patients.

More Information

Please visit the following links for more information about

Venous thromboembolism: https://www.cdc.gov/ncbddd/dvt/index.html

Hospital-associated venous thromboembolism: https://www.cdc.gov/ncbddd/dvt/documents.html

Paper Reference

Tsai J, Grant AM, Beckman MG, Grosse SD, Yusuf HR, Richardson LC. (2015) Determinants of Venous Thromboembolism among Hospitalizations of US Adults: A Multilevel Analysis. PLoS ONE 10(4): e0123842. doi:10.1371/journal.pone.0123842.