title: Comparison of factor VIII-related antigen and erythrocyte sedimentation rate in outpatient management of vasculitis.
abstract: Electroimmunodiffusion (Laurell rocket) determinations of factor VIII-related antigen in plasma were ordered to determine the cost/benefit ratio for factor VIII-related antigen as a putative test for endothelial damage in suspected vasculitis. Twenty-seven consecutive patients referred for vasculitis or suspected vasculitis were identified and followed up for an average of 9.1 +/- months (range: one to thirty-three months) in a prospective, unblinded study performed in a clinic, associated with a 1054-bed inner-city university hospital. There was no difference in Westergren erythrocyte sedimentation rate (WESR) in patients with final diagnosis of systemic vasculitis (SV) (38 +/- 12 mm/hour) compared to those without vasculitis (NV) (27 +/- 7) as the final diagnosis. The mean plasma concentration of factor VIII-related antigen was significantly elevated in SV (344 +/- 100%) when compared with NV (147 +/- 39%) (P < 0.016). The factor VIII-related antigen test in this study was 2.56 times more likely (crude odds ratio) than the WESR to contribute to a change in diagnosis or therapy (P = 0.016). Positive and negative predictive values (PPV and NPV) for factor VIII-related antigen (abnormal at greater than 220% of the normal value) were both 70%. PPV and NPV for WESR were 56% and 86%, respectively. The factor VIII-related test was less cost-effective than the WESR in the follow-up period unless it was important to define complete remission or differentiate vasculitis flare from infection. The authors conclude that factor VIII-related antigen is a useful test in the initial diagnosis of vasculitis.
authors.affiliation: Division of Rheumatology, Allergy & Immunology, Medical College of Virginia, Virginia Commonwealth University, Richmond, USA.
authors.forename: W N
authors.initials: WN
authors.lastname: Roberts
authors.forename: J P
authors.initials: JP
authors.lastname: Brodeur
authors.forename: J
authors.initials: J
authors.lastname: DeWitt
authors.forename: S Z
authors.initials: SZ
authors.lastname: Carr
authors.forename: C M
authors.initials: CM
authors.lastname: Wise
authors.forename: M E
authors.initials: ME
authors.lastname: Carr
mesh_terms: D000553:Ambulatory Care; D001799:Blood Sedimentation; D005169:Factor VIII / Q000032:analysis*; D014890:Granulomatosis with Polyangiitis / Q000276:immunology; D006801:Humans; D011446:Prospective Studies; D014657:Vasculitis / Q000175:diagnosis*
chemical_list: D005169:Factor VIII