Activated coagulation assay could rule in DVT diagnosis
MedWire News: Study findings suggest that a novel marker of activated coagulation, in combination with D-dimer testing, could be used to help rule in a diagnosis of deep vein thrombosis (DVT).
D-dimer tests are effective, in conjunction with clinical probability logarithms, for ruling out DVT in up to 50% of patients, but have a low specificity and positive predictive value (PPV), explain Johan Elf (Lund University Hospital, Sweden) and co-workers.
In addition, D-dimers are poorly defined and tests measure a range of different degradation products, hindering comparisons between clinical trial results, they say.
Writing in the Journal of Thrombosis and Thrombolysis, the team suggests that these issues may be overcome by use of a novel marker of activated coagulation, the Activated Protein-C in complex with Protein-C inhibitor (APC–PCI complex). APC–PCI complex is a well-defined analyte, allowing direct trial comparisons, and a test is now commercially available.
To investigate, the researchers examined 350 frozen plasma samples from outpatients with suspicion of DVT using two D-dimer tests and the APC–PCI complex assay.
DVT was assessed using clinical probability scores, venous ultrasound, and contrast venography. The prevalence of low, intermediate, and high clinical probability of DVT was 44%, 39%, and 16%, respectively, and DVT was confirmed in 23% of patients, made up of 8.4% of low-probability and 34.9% of intermediate- or high-probability patients.
The APC–PCI complex assay was inferior to the D-dimer tests in terms of sensitivity (74% vs >93%), negative predictive value (91% vs >96%), and area under the curve (0.82 vs 0.90).
However, the APC–PCI complex assay offered significantly higher specificity than the D-dimer assays (80% vs 40–60%), as well as higher PPV for intermediate–high-probability patients (66% vs <52%).
When combined with a D-dimer assay, using an APC–PCI cutoff of 500 ng/ml in intermediate–high-risk patients confirmed DVT diagnosis in 93% of 44 patients assessed.
While recognizing that further work on the cutoff level for excluding DVT with APC–PCI assay is required, Elf et al conclude: “High levels of D-dimers and APC–PCI complex can help to rule DVT in.”
They add: “The clinical importance of this needs further prospective evaluation in management studies.”
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By Lynda Williams