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Urine test can identify venous thromboembolism

Venous thromboembolism can be detected through the use of a simple urine test, according to a new study.

Urine test can identify venous thromboembolism

Researchers from California and Canada found the test evaluates the levels of fibrinopeptide B (FPB) in the body − a small peptide that is released when a thrombosis forms and is removed through urine.

“The urine FPB test offers advantages over other screening methods”

Timothy Fernandes

They used stored urine samples taken from 344 patients who participated in a separate multicentre analysis of 1,417 patients considered likely to have an acute pulmonary embolism.

FPB concentration was measured in each of the samples, while the sensitivity and specificity of the test was evaluated at various cut-off points in relation to its ability to predict the presence of venous thromboembolism.

Timothy Fernandes

Timothy Fernandes

Urine FPB was found to demonstrate sensitivity comparable to previously published values for plasma latex and whole blood D-dimer levels at concentrations of 2.5ng/ml, but with greater specificity.

Timothy Fernandes, the lead author of the study, concluded that the urine FPB test can provide more accurate results than the D-dimer test because it does not require blood to be drawn from the body.

This means the FPB test can reflect ongoing clot activity, while D-dimer can only be measured once a clot has already become degraded.

“The urine FPB test offers advantages over other screening methods because it doesn’t require blood to be drawn and it can provide more accurate results than the D-dimer test,” he said.

The results of the study will be presented at the American Thoracic Society’s 2014 International Conference in San Diego.

 

Study Abstract

Urine Fibrinopeptide B As A Screening Test For Acute Pulmonary Embolism
Authors: T.M. Fernandes1, D. De Santis1, P.G. Chiles1, J.J. Marsh1, P.S. Wells2, T.A. Morris1; 1University of California, San Diego - La Jolla, CA/US, 2The Ottawa Hospital and the University of Ottawa - Ottawa, ON/CA

Introduction: Fibrinopeptide B (FPB) is a small peptide released from fibrinogen during the thrombin-catalyzed conversion to fibrin during thrombosis and then rapidly cleared in the urine. A pilot trial suggested that urine FPB levels could screen patients for venous thromboembolism. We validated the sensitivity, specificity and likelihood ratios for several diagnostic thresholds of urine FPB on stored samples from the prospective Pulmonary Embolism Diagnosis Study (PEDS).

Methods: The PEDS multicenter study randomized 1417 patients considered likely to have acute pulmonary embolism based on a Wells clinical model score of 4.5 or greater or a positive D-dimer assay result. Pulmonary embolism was confirmed or ruled out by objective criteria. For the current study, we obtained urine samples at the time of study enrollment from a subset of patients in the parent study. We measured the concentration of FPB by competition ELISA. We evaluated the sensitivity, specificity and negative likelihood ratio for three threshold levels of urine FPB: 2.5 ng/ml, 5 ng/ml and 7.5 ng/ml.

Results: The study group consisted of 344 patients: 61 (18%) with pulmonary embolism and 283 (83%) without. At a threshold of 2.5 ng/ml, urine FPB demonstrated sensitivity of 75.4% (95% CI: 62.4-85.2%), specificity of 28.9% (95% CI: 23.8-34.7%), and negative likelihood ratio of 0.18 (0.11-0.29), 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% (95% CI: 42.5-68.2%), and 42.6% (30.3-55.9%), respectively.

Conclusion: In this population of patients with moderate to high probabilities of pulmonary embolism, 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. Urine FPB tests do not require phlebotomy and, in contrast to D-dimer test, reflect ongoing thrombosis directly. Urine FPB tests may be a useful compliment to current biomarkers for the presence and activity of venous thromboembolism.

Readers' comments (1)

  • I'm sorry, but a test that only gets it right <30% of the time when someone does not have the condition is not a good test. That means 70% of people without a VTE test as positive for VTE, and 25% with VTE test as negative. Given that most people tested for VTE don't have a VTE, that means most positive results are for people without a VTE. In the research group, 46 of the 61 with VTE had a positive result (that's what 75.4% sensitivity means), the other 15 got a negative result. Of the 283 who did not have VTE 198 had a positive test result (28.9% specificity means only 28.9% of negative people got a negative result). In other words 244 patients had a positive result, but only 46 actually were positive for VTE, so 81.1% of all positive test results were for patients without VTE. And the D-dimer test is even worse.

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