The Prevalence of von Willebrand Disease in the Primary Care Setting.

Von Willebrand Disease (VWD), the most common inherited bleeding disorder in humans, results from a deficiency or abnormal functioning of von Willebrand factor (VWF). The most widely accepted estimate of VWD prevalence in the literature is 1%, which is derived from epidemiological studies performed in the USA and Italy. However, both of these studies were based on investigations of healthy, school aged children without overt bleeding symptoms. In contrast, the prevalence of symptomatic VWD has been estimated to be approximately 1 in 10,000 based on patients referred to specialized bleeding clinics. The discrepancy between these prevalence figures has not been explained and requires further investigation. This uncertainty is further complicated by a lack of consensus concerning the frequency of bleeding symptoms in the normal population. VWD can cause a range of symptoms from mild bruising to significant mucocutaneous bleeding. Such symptoms are often presented to primary care physicians by their patients but are not always significant enough to prompt a referral to a specialist. Thus, the primary care setting provides a unique context for assessing the prevalence of symptomatic VWD. The objective of the present study is to perform a prospective assessment of the prevalence of symptomatic VWD in the primary care setting. The on-going study has been carried out since September 2004 in four primary care clinics in the Kingston, Ontario area. Patients of all ages were approached in the waiting rooms of the clinics and asked if they had ever experienced problems with bleeding or bruising. Those that were significantly concerned by their symptoms and not aware of the cause of their bruising or bleeding (e.g. oral anticoagulant therapy) were then eligible to complete a detailed standardized bleeding questionnaire adapted from that used in the recent European multicenter type 1 VWD study (MCMDM-1VWD). The questionnaires were scored in terms of the severity and frequency of the following symptoms: epistaxis, bruising, oral cavity bleeding, post-dental extraction bleeding, gastrointestinal bleeding, post-operative bleeding, menorrhagia, post-partum hemorrhaging, hemarthrosis and central nervous system bleeding. Subjects with a positive score of five or greater on the questionnaire were then sent for VWD laboratory studies on two separate occasions, at least 4–6 weeks apart. To date, 5,000 patients have been approached and asked if they have ever experienced problems with bruising or bleeding. Of those, approximately 11% reported problems with bruising or bleeding, a number significantly lower than the 25% reported in the literature. Only 104 patients reported significant symptoms and 45 people went on to complete the bleeding questionnaire. Approximately 53% of the subjects had a positive bleeding score leading to laboratory investigations for VWD. Of the subjects that have had blood work performed, we have made a new diagnosis of type I VWD in one individual. As well, three patients approached at the clinics had been previously diagnosed with VWD. Therefore, the prevalence of symptomatic VWD in the primary care setting evaluated thus far in this study is 0.08%.