From FD Patel, MD: I had a patient here who was tested for both FDP and D-dimer. Her D-dimer was mildly elevated at 0.79 but her fibrin degradation products (FDP) assay result was undetectable. Since the D-dimer is a type of fibrin split product, how can you explain this discrepancy? I’m thinking it has something to do with what each test measures, but would like to be sure. thank you.
Hello, Dr. Patel, and thank you for your question. Most D-dimer assays are considerably more sensitive than the FDP (fibrin degradation or fibrin split products) assay, explaining why the D-dimer may be positive while the FDP is negative. You may wish to consider deferring the FDP assay in the future, considering it is the less sensitive of the two and they measure the same thing. If your patient develops disseminated intravascular coagulation (DIC), both will be strongly positive. Geo.