Abstract
A potential complement to existing biomarkers of venous thromboembolism, fibrinopeptide B (FPB) is readily available in urine, unlike D-dimer, which must be obtained from blood. Besides helping patients avoid extra blood draws, FPB can give physicians a more complete picture of clot activity. FPB, a small peptide, is released when a thrombosis forms, whereas D-dimer, a protein fragment generated via fibrinolysis, is present in the blood only after a clot starts to degrade. Also, as demonstrated by researchers based at the University of California, San Diego, FPB has the potential for greater specificity.
These findings were reported at the American Thoracic Society's 2014 International Conference, which took place May 16–21. The researchers, led by Timothy Fernandes, M.D., M.P.H., described how they conducted a pilot trial and evaluated FPB as a screening test for venous thromboembolism.
The researchers used stored urine samples taken from 344 patients who participated in the Pulmonary Embolism Diagnosis Study (PEDS), a multicenter study of 1,417 patients considered likely to have an acute pulmonary embolism. For all urine samples, the researchers measured the FPB concentration by competition ELISA and evaluated the sensitivity and specificity of the test at various cut-off points in relation to its ability to predict the presence of venous thromboembolism.
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At a threshold of 2.5 ng/mL, urine FPB demonstrated sensitivity of 75.4%, specificity of 28.9%, and negative likelihood ratio of 0.18, weighted by prevalence in the sample population. However, the thresholds of 5 ng/mL and 7.5 ng/mL had sensitivities of only 55.7%, and 42.6%, respectively.
The researchers concluded that in their patients, urine FBP at a threshold of 2.5 ng/mL demonstrated sensitivity comparable to previously published values for plasma latex and whole blood D-dimer levels, but with greater specificity.
“The results of our study indicate that urine FPB tests may be a useful complement to current biomarkers such as D-dimer to measure for the presence and activity of venous thromboembolism,” Dr. Fernandes said. “As an addition to other types of testing, FPB urine provides greater specificity and doesn't require a blood draw, which can be a major boon to patients.”
Dr. Fernandes and his colleagues plan to develop a urine dipstick test for FBP that could be quickly and widely applied. Future studies are planned to assess urine fibrinopeptide B in other settings where D-dimer is used including use of urine fibrinopeptide after anticoagulation to determine the risk of recurrent venous thromboembolism.