Reduced Mobility Often Overlooked in Blood Clot Risk Assessments

Study found one-third of hospitalized patients were misclassified according to VTE risk and half did not receive proper treatment received inappropriate treatment

(WASHINGTON, May 15, 2025) — A study released today in Blood Advances found that admitting physicians did not accurately classify the risk for blood clots for one in three medical patients, leading to inappropriate treatment for half of patients.

Blood clots, also known as venous thromboembolism (VTE), are a serious medical condition that can cause disability and even death. Inaccurate assessment of VTE risk factors, particularly reduced mobility, can result in patients not receiving essential and potentially lifesaving VTE prophylaxis, or preventive treatment, and can lead to bleeding episodes in patients unnecessarily receiving prophylaxis.

“The admission process is hectic, and the primary focus of an admitting physician is the problem bringing the patient to the hospital,” said study author Michael Streiff, MD, professor of medicine at Johns Hopkins School of Medicine. “As such, it can be difficult for them to accurately determine the patient’s risk of VTE, especially with the limited information they have on hand.”

VTE is the third most common blood vessel disorder, affecting about one million Americans each year. The condition can be disabling or even life-threatening, with blood clots in the lung linked to roughly one in ten hospital deaths. It can manifest as deep vein thrombosis, when a blood clot forms in a vein in the arms or legs, or pulmonary embolism, when a blood clot blocks an artery in the lung. Typically, during a patient’s admission to the hospital, the admitting physician conducts a VTE risk assessment to determine the patient’s risk of developing blood clots. Based on this assessment, the physician may prescribe any necessary prophylaxis, such as oral anticoagulants or compression socks.

In the first study to evaluate the accuracy of provider-assessed VTE risk and its impact on outcomes in hospitalized patients, Dr. Streiff and his team analyzed the VTE risk assessment data of 4,021 patients consecutively hospitalized at the Johns Hopkins Hospital between January 1 to April 30, 2019. All patients were initially evaluated for VTE risk by their admitting physicians using the Padua Prediction Score, a points-based model commonly used to identify individuals at high risk of VTE. A subject matter expert then used the same model to retrospectively review all patient charts and complete independent risk assessments.

Of the 4,021 patients included in the study, admitting providers identified 1,058 (26.3%) as high risk for VTE and 2,963 (73.7%) as low risk. In comparison, the expert identified 1,974 (49.1%) patients from the cohort as high risk for VTE and 2,047 patients (50.9%) as low risk. Overall, the expert found that 1,396 (34.7%) patients were misclassified by their admitting providers, leading to inappropriate VTE prophylaxis in about half of patients.

“The expert agreed with the admitting physicians’ assessments only about 65% of the time and often found patients to be at a higher risk for blood clots than the physicians did,” said Dr. Streiff. “When we further examined this data, we found that, of the 36 patients who developed a blood clot during their hospital stay, 21 were inaccurately determined to be at low risk for VTE. Additionally, for the 13 patients we found who experienced bleeds while on prophylaxis, seven were low risk for VTE and should not have been receiving preventive care.”

The researchers determined that the VTE risk factors most missed by providers upon admission included respiratory or heart failure, reduced mobility, and acute infection or rheumatologic disorder. In the Padua risk assessment model, immobility is one of the most heavily weighted factors and can significantly impact whether a patient is ultimately deemed low or high risk for VTE.

Dr. Streiff and his team recommended that VTE risk assessment tools incorporate and auto-populate data from patients’ electronic health records to streamline the process for admitting physicians and improve patient outcomes. Additionally, they emphasized the importance of evaluating mobility throughout a patient’s hospital stay, not just upon admission.

“Patient mobility is a very potent risk factor, but nurse assessments of mobility tend to be more accurate, as they have the opportunity to interact with patients multiple times during their shifts,” said Dr. Streiff. “This data should be given to providers to inform mobility assessments and potential changes in a patient’s risk profile.”

The study has several limitations, predominantly that it was conducted retrospectively and at a single center. Additionally, the expert was able to inform their VTE risk assessment with mobility data documented throughout hospitalization, which were unavailable to admitting physicians. Johns Hopkins also uses a Padua score cutoff of 3 to categorize patients as high risk for VTE, though the standard threshold is 4.

Dr. Streiff and his team are currently developing an improved risk assessment tool for use at Johns Hopkins Hospital.

Blood Advances (bloodadvances.org) is an online, open-access journal publishing more peer-reviewed hematology research than any other academic journal worldwide. Blood Advances is part of the Blood journals portfolio (bloodjournals.org) from the American Society of Hematology (ASH) (hematology.org).

Claire Whetzel, 202-629-5085
cwhetzel@hematology.org