Please consult pathologist or haematologist if testing abnormal.
The findings of the above tests are interpreted together, in conjunction with the family and bleeding history. VWD is classified into three major types:
Type 1 VWD – a partial quantitative deficiency of VWF.
Type 2 VWD – a qualitative abnormality as demonstrated by VWF multimer studies, RIPA, ratio of VWF activity to antigen ratio, or other special assays.
Type 2 VWD is classified into four subtypes:
2A – Decreased VWF-dependent platelet adhesion with selective deficiency of high-molecular-weight multimers
2B – Increased affinity for platelet GPIb
2M – Decreased VWF-dependent platelet adhesion without selective deficiency of high-molecular-weight multimers
2N – markedly decreased binding affinity of FVIII
Type 3 VWD – virtually complete deficiency of VWF
Acquired von Willebrand syndrome may occur when there are defects in VWF concentration or function due to other medical disorders (such as autoimmune disorders, lymphoproliferative disease, monoclonal gammopathies, hypothyroidism, cardiovascular lesions and myleoproliferative and some other neoplasms).
Systemic inflammation, pregnancy, oral contraceptives and stress may increase plasma levels of VWF and mask lower baseline levels. Therefore repeated testing is sometimes required to identify low levels. ABO blood group also has an effect of VWF levels, with lower levels in individuals with blood group O compared with other blood group types.