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Willebrand disease

Von Willebrand's disease (vWD) is the most common hereditary coagulation abnormality described in humans. It arises from a qualitative or quantitative deficiency of von Willebrand factor (vWF), a multimeric protein that is required for platelet adhesion. It is known to affect humans and, in veterinary medicine, dogs. more...

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Symptoms

The various types of vWD present with varying degrees of bleeding tendency. Severe internal or joint bleeding is rare (only in type 3 vWD); bruising, nosebleeds, heavy menstrual periods (in women) and blood loss during childbirth (rare) may occur.

Diagnosis

When suspected, blood plasma of a patient needs to be investigated for quantitative and qualitative deficiencies of vWF. This is achieved by measuring the amount of vWF in a vWF antigen assay and the functionallity of vWF with a glycoprotein (GP)Ib binding assay, a collagen binding assay or, a ristocetin cofactor (RiCof) activity assay. Factor VIII levels are also performed as factor VIII is bound to vWF which protects the factor VIII from rapid break down within the blood. Deficiency of vWF can therefore lead to a reduction in Factor VIII levels. Normal levels do not exclude all forms of vWD: particularly type 2 which may only be revealed by investigating platelet interaction with subendothelium under flow (PAF), a highly specialistic coagulation study not routinely performed in most medical laboratories. A platelet aggregation assay will show an abnormal response to ristocetin with normal responses to the other agonists used. A platelet function assay (PFA) will give an abnormal collagen/adrenaline closure time but a normal collagen/ADP time. Type 2N can only be diagnosed by performing a "factor VIII binding" assay. Detection of vWD is complicated by vWF being an acute phase reactant with levels rising in infection, pregnancy and stress.

Other tests performed in any patient with bleeding problems are a full blood count (especially platelet counts), APTT (activated partial thromboplastin time), prothrombin time, thrombin time and fibrinogen level. Testing for factor IX may also be performed if hemophilia B is suspected. Other coagulation factor assays may be performed depending on the results of a coagulation screen.

Classification and types

Read more at Wikipedia.org


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Menorrhagia and screening for von Willebrand disease
From American Family Physician, 5/15/05 by Anne D. Walling

Menorrhagia is a significant health problem for women of reproductive age and was responsible for nearly 98,000 hospital admissions in the year 2000. Among the various causes of menorrhagia, coagulation disorders are particularly serious because they can increase the risks of surgical treatment. The most common coagulation disorder, yon Willebrand disease, has an estimated prevalence of 5 to 20 percent in women with menorrhagia, compared with less than 1 percent in other women. In 2001, the American College of Obstetricians and Gynecologists recommended screening for von Willebrand disease in adolescents with menorrhagia, women in whom a cause for menorrhagia cannot be established, and women undergoing hysterectomy for menorrhagia. However, the evidence behind this recommendation is controversial. James and colleagues conducted a systematic review of relevant studies to determine the value of screening for von Willebrand disease in women with menorrhagia.

An initial search of electronic databases, abstracts of conferences, and bibliographies, in addition to consultation with experts, identified more than 150 items. After independent review, 107 articles, published from 1990 to 2003, were selected for inclusion in the study. Five articles concerned the prevalence of von Willebrand disease in women with menorrhagia, differing in the populations studied and definitions of the disease and condition. These studies involved between 19 and 150 women and provided prevalence estimates of between 5.3 and 20 percent. The confidence intervals in each studywere high (e.g., 7.9 to 18.8 percent and 4.0 to 14.2 percent for the two largest).

Studies on the impact of von Willebrand disease and menorrhagia on quality of life also differed considerably in the definitions and measures used. These studies indicate that von Willebrand disease with menorrhagia has a significant negative impact on quality of life, but no data were identified to suggest that this impact is worse than that of menorrhagia alone. Only three studies, with a total of 29 patients, addressed any increased risk of surgery in women with von Willebrand disease, and data were limited further by the uncertainty of case identification.

The authors also reviewed articles on screening tests for von Willebrand disease. Several tests are available and estimates of the sensitivity and specificity of each one vary. Comparisons between the tests could not be made from the available data; thus the most effective test was not determined.

The authors conclude that although von Willebrand disease may be more prevalent in women with menorrhagia than in the general population, it is difficult to identify the proportion of menorrhagia cases attributable to this disease. In addition, there are too few data to confirm the degree of enhanced morbidity or surgical risk in women who have menorrhagia with von Willebrand disease. Routine screening for von Willebrand disease in women with menorrhagia therefore is not supported sufficiently by current evidence. Further data are needed.

James A, et al. Testing for von Willebrand disease in women with menorrhagia: a systematic review. Obstet Gynecol August 2004;104:381-8.

COPYRIGHT 2005 American Academy of Family Physicians
COPYRIGHT 2005 Gale Group

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