Factor V Leiden is a blood clotting disease that is present or not, it is a genetic defect so that means that the disease is hereditary. Factor V is the protein that causes blood clotting. Leiden was added because the disease was first discovered in the city of Leiden. The Factor V protein is over active, so that it does not stop clotting in time and blood clots form in the veins. This condition occurs in less than 8 percent of the population in the Netherlands. The most common symptoms are cramps and pain in expected and unexpected places, such as the back of the knee, in the groin or on the chest.

The PCR kit can diagnose Factor V Leiden by analyzing gene 1691. The genetic abnormality takes place on this gene, instead of nucleotide G being present there, nucleotide A is present. This mutation ensures over expression of the protein Factor V, the moment either the mutation or the overexpression is measured, the diagnosis of factor V Leiden can be made.