PLASMA-LEVELS OF VON-WILLEBRAND-FACTOR ANTIGEN IN ACUTE BRONCHITIS AND IN A NORMAL POPULATION

von Willebrand factor (vWF) is a large glycoprotein secreted predomina ntly by endothelial cells in both the systemic and pulmonary circulati ons and has a central role in the formation of the platelet plug. It h as been put forward as a possible marker of endothelial cell injury, b ut is not ideal in that it is not specific for either the pulmonary or systemic circulation and may be released as part of the acute phase r esponse from otherwise healthy endothelial cells. We undertook two stu dies (i) to assess within-subject variation in plasma von Willebrand f actor antigen (vWF:Ag) levels over time and to assess between-subject variation in a healthy patient population, and (ii) as part of a descr iptive study of acute bronchitis, to assess whether plasma vWF:Ag leve ls altered in such a common and minor insult. A random sample of patie nts aged 45-74 years were taken from a local general practice. vWF:Ag levels were measured on three occasions, and spirometry was performed. The descriptive study was undertaken on patients in the general pract ice diagnosed with acute bronchitis without pre-existing pulmonary dis ease. Plasma vWF:Ag was measured on presentation and 14 and 42 days la ter. In 219 randomly selected patients the mean plasma vWF:Ag was simi lar at all three visits, the within-subject standard deviation bring 0 .09 U ml(-1). vWF:Ag levels rose significantly with age (r(2)=0.29, P< 0.01). In 39 patients with acute bronchitis, the plasma vWF:Ag level a t presentation (1.51 U ml(-1)) was significantly higher than at 2 and 6 weeks later (1.06 U ml(-1) and 1.12 U ml(-1) respectively). There wa s no correlation between plasma vWF:Ag and C-reactive protein on prese ntation. We conclude that there is relatively little variation in an i ndividual's plasma vWF:Ag level but that levels increase significantly with age. The observed elevation occurring with acute bronchitis is a true phenomenon; the absence of an associated acute phase response su ggests that endothelial cell injury is the mechanism for the rise. The se observations are important in the context of vWF as a marker of end othelial cell damage, as a common and supposedly minor insult such as acute bronchitis may markedly raise plasma levels.