D-dimer is a protein fragment formed by the breakdown of fibrin in the body. It is a marker for disseminated intravascular coagulation (DIC) and can also be positive in patients with deep vein thrombosis and pulmonary embolisms. Recently, D-dimer has been used as a predictor for the severity and mortality of Covid-19, due to lung damage caused by the virus, resulting in pulmonary embolisms.
D-Dimer has been shown to increase with age, leading to a lower specificity (more false positives) in populations with advanced age. With individuals older than eighty years, the specificity is 0-18% and this should be considered during patient diagnosis. D-dimer is also not a good choice for hospitalized patients, patients with recurrent venous thromboembolisms, patients with high degrees of inflammation, or pregnant patients, as the specificity for the assay is too low.
At Solaris Diagnostics, D-dimer is detected through a turbidimetric methodology. Polystyrene particles coated with a monoclonal antibody aggregate in the presence of D-dimer, causing an increase in turbidity, which is then measured. Samples for D-dimer are collected in blue-top sodium citrate tubes with turn around time 24 hours from the time it is received in the laboratory.