From the Guidelines
Obese patients often have elevated D-dimer levels, even in the absence of thrombotic disease, due to chronic inflammation and altered coagulation factors associated with obesity. This elevation can lead to "positive" D-dimer results when standard cutoff values are used, reducing the test's specificity in this population and potentially leading to unnecessary additional testing 1. The use of D-dimer for diagnosing thrombosis is noteworthy, but its positive predictive value is low in many clinical settings where venous thromboembolism incidence is low 1. However, in severe cases, such as COVID-19 patients with a high burden of thrombotic complications, a D-dimers level > 5 mg/mL is associated with a remarkably high thrombotic risk, with a positive predictive value of at least 40–50% 1.
- Key points to consider:
- Obesity is associated with a chronic inflammatory state and altered coagulation factors that can lead to baseline D-dimer elevations 1.
- The positive predictive value of D-dimer testing is low in many clinical settings where venous thromboembolism incidence is low 1.
- Some experts suggest using weight-adjusted D-dimer cutoffs or higher threshold values for obese patients to improve the test's clinical utility 1.
- Clinicians should consider the baseline elevation of D-dimer in obese patients and incorporate clinical probability assessment tools like Wells or Geneva scores to guide management decisions rather than relying solely on D-dimer values 1. When interpreting D-dimer results in obese patients, clinicians should use a higher threshold value, such as > 5 mg/mL, and incorporate clinical probability assessment tools to guide management decisions. This approach can help improve the test's clinical utility and reduce unnecessary additional testing in this population 1.
From the Research
D-Dimer Levels in Obese Patients
- The relationship between obesity and D-dimer levels is complex, with some studies suggesting a positive correlation between the two 2.
- A study published in 2011 found that D-dimer levels were positively correlated with waist-to-hip ratio (WHR) in female patients, but not in male patients 2.
- However, another study published in 2010 found that body mass index (BMI) was not a significant predictor of positive D-dimer results in patients evaluated for pulmonary embolism 3.
- A 2021 study found that elevated plasma D-dimer levels were associated with an increased risk of incident venous thromboembolism (VTE), but the risk estimates were attenuated after adjusting for BMI and C-reactive protein (CRP) 4.
Obesity as a Risk Factor for Venous Thromboembolism
- Obesity is a known risk factor for venous thromboembolism (VTE), but the relationship between obesity and D-dimer levels is not fully understood 5, 4.
- A 2024 study found that BMI and obesity were not associated with confirmed pulmonary embolism (PE) in patients with suspected PE, and the age-adjusted D-dimer strategy appeared safe in ruling out PE in obese patients with suspected PE 5.
- Another study published in 2015 found that an elevated D-dimer was independently associated with an increased risk for incident VTE, recurrent VTE, and mortality 6.
D-Dimer as a Biomarker
- D-dimer is a biomarker of fibrin formation and degradation, and elevated levels are associated with an increased risk of adverse outcomes, including VTE and mortality 6, 4.
- The use of D-dimer as a diagnostic tool is limited by its low specificity, and many factors can affect D-dimer levels, including age, sex, and comorbidities 3.