What is the role of lab tests in the workup of venous thromboembolism (VTE)?

Updated: Nov 05, 2020
  • Author: Vera A De Palo, MD, MBA, FCCP; Chief Editor: Vinod K Panchbhavi, MD, FACS  more...
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Answer

Arterial blood gas assessment on room air demonstrates hypoxemia (arterial oxygen tension [PaO2] < 80 mm Hg) and an elevated alveolar-arterial oxygen gradient. Acid-base status may demonstrate a respiratory alkalosis.

Enzyme-linked immunoassay (ELISA) can be used to quantify the presence of D-dimer, which is a specific degradation product of cross-linked fibrin. [21] This is an important marker of the activation of fibrinolysis. It can be elevated in pneumonia, cancer, sepsis, and surgery.

A plasma D-dimer level higher than 500 ng/mL has been shown to have a sensitivity of 97% and a specificity of 45%. The value of D-dimer is in its negative predictive value. A plasma D-dimer level lower than 500 ng/mL in those with low pretest probability essentially excludes pulmonary embolism (PE).

This study is less helpful in older patients, in that the D-dimer level tends to increase with age. In a study by Righini et al, an age-adjusted D-dimer cutoff combined with a probability assessment was shown to rule out the diagnosis of PE in emergency department (ED) patients with suspected PE and was associated with a low likelihood of subsequent symptomatic VTE, thus increasing the proportion of patients in whom the diagnosis could be excluded. [22]

Elevated troponins are associated with an adverse prognosis in acute PE. [23] Elevated natriuretic peptides, brain natriuretic peptide (BNP), and N-terminal pro-BNP have been shown to be predictive of adverse short-term outcomes in acute PE and can be predictive of mortality. [24, 25] Measurement of both troponin and BNP are important for risk stratification in patients with PE.

Bilirubin levels may also assist in the diagnosis of VTE. In a study that included 103 patients with VTE (distal DVT, proximal DVT, or PE) and 50 control subjects, Duman et al found that in comparison with the control group, the VTE group had a lower bilirubin level (9.0 ± 2.6 μmol/L vs 7.3 ± 3 μmol/L), a higher high-sensitivity C-reactive protein (hs-CRP) concentration (0.8 [0.3-2] mg/L vs 1.1 [0.2-3] mg/L), and a higher white blood cell (WBC) count (7.4 ± 1.5 ×109/L vs 8.2 ± 2.7 × 109/L). [26]


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