Fig. 3-D Model of D-dimer. [Credit: StudioMolekuul. Shutterstock]
Disclaimer: This substack entry contains informal musing about variety of scientific issues. It is a messy notebook by design. Hence by its very nature it is bound to include errors, inaccuracies, omissions and other blemishes. Please keep it in mind while reading.
D-DIMER DILEMMAS.
D-dimer is a peculiar test. It was always misused and had a rather bad press in academic medicine even before vaccination VITT story.
This table shows the place of D-dimer among other coagulation tests [Credit UTD 2022]:
And here is a nice summary of many causes and mechanisms of D-dimer elevation [Credit: UTD 2022]:
The prognostic value for COVID Infection course of d-dimer is solidly documented but it’s use outside of this area and traditional application (see below) is still TENUOUS at best.
Fibrin D-dimer is one of the major fibrin degradation products released upon cleavage of crosslinked fibrin by plasmin.
The dimer consists of two D domains from adjacent fibrin monomers that have been crosslinked by activated factor XIII.
Normal plasma levels of D-dimer by ELISA testing are <500 ng/mL for fibrin equivalent units (FEU) or <250 ng/mL for D-dimer units (DDU).
Elevated concentrations of plasma D-dimer indicate recent or ongoing intravascular coagulation and fibrinolysis.
Plasmin cleaves crosslinked fibrin at multiple sites, generating other fibrin degradation products (FDPs), but D-dimer is the best-studied and validated for clinical assessment. Yet, clinical uses of the D-dimer is quite limited and include evaluation for the following:
Deep vein thrombosis
Pulmonary embolism - the most classic use.
Evaluation and management of disseminated intravascular coagulation (DIC)
Primary hyperfibrinolysis occurring in variety of Thrombotic and hemorrhagic disorders due to intrinsically abnormal fibrinolysis
Prognostic assessment in coronavirus disease 2019 (COVID-19) a novel but well documented use for COVID-19: Hypercoagulability states.
While the DISSIDENT MEDICINE is abuzz about the d-dimer for assessment of potential vaccinations’ side effects the theory given by the proponents is rather flimsy and stems likely from misinterpretation of published VITT diagnostic measures.
Officialdom Medicine explicitly states that: “ as noted in an expert consensus document - the evidence does not support any screening laboratory (d-dimer) or imaging evaluations in individuals before or after vaccination in patients without the clear symptoms or signs of thrombosis ”
This is a work in progress so stay tuned…