Paul Smith writes, “I have a family member on Xarelto and his D-dimer reference range was 450 while taking Xarelto. What is the reference range?
Hello, Mr. Smith, and thank you for your question. There is some mild confusion about the D-dimer reference intervals (reference ranges) because several distributors use varient methods. These methods result in two distinct reference intervals that are reported in D-dimer units (DDUs) and in fibrinogen equivalent units (FEUs). About 70% of labs use the method that reports in FEUs. We only report the high limit of the interval because a low D-dimer has no clinical meaning. The DDU limit is typically 240 ng/mL and the FEU limit is 500 ng/mL. The actual numbers vary among laboratories because each laboratory director is required to carefully vaildate based on their local healthy population. Examine your family member’s lab report to confirm whether his/her lab is using DDUs or FEUs.
We had a thorough discussion about age-adjusted D-dimer in 2014, and many physicians use age times 10 for people over 50, thus at age 60 the limit would be 600 ng/mL FEUs and at 70, 700 ng/mL FEUs. We don’t have published age-adjusted levels for DDUs.
If your relative’s D-dimer result is normal, meaning below the limit, the result may be used to rule out deep vein thrombosis (a clot in a leg vein) or pulmonary embolism, (clot in the lung). D-dimer results above the reference limit are not diagnostic, as several non-specific forms of inflammation mey elevate the level. There is no evidence that suggests Xarelto or any of the anticoagulants (blood thinners) affect the D-dimer result.
I hope this answers your question, and watch here for comments from our various expert participants.