title: Factor XIII in primary antiphospholipid syndrome.
abstract: OBJECTIVE
  To evaluate the clinical significance of factor XIII (FXIII) in primary antiphospholipid syndrome (APS).
  
  
  METHODS
  A cross-sectional study including patients with primary APS (n =29), persistent carriers of idiopathic antiphospholipid antibodies (aPL) with no history of thrombosis (n = 14), thrombotic patients with inherited thrombophilia (n =24), healthy controls (n =28), and patients with mitral and aortic valve prosthesis (n =32, as controls for FXIII only). FXIII and fibrinogen were measured by functional assays: IgG anticardiolipin antibody (aCL), IgG anti-beta2-glycoprotein I (anti-beta2-GPI), and plasminogen activator inhibitor (PAI) by immunoassay; and paraoxonase activity by paranitrophenol formation. Intima-media thickness (IMT) of carotid arteries was determined by high resolution sonography.
  
  
  RESULTS
  FXIII activity (FXIIIa) was highest in primary APS (p= 0.001), particularly in patients with multiple occlusions (n =12) versus those with single occlusion (158 +/- 45% vs 118 +/- 38%; p=0.02). In primary APS, FXIII positively correlated with PAI (p=0.003) and fibrinogen (p = 0.005). Similarly in the thrombotic control group, FXIIIa correlated with PAI (p =0.05) and fibrinogen (0.007). In primary APS, FXIIIa was related to the IMT of all carotid artery segments (p always < 0.01). In thrombotic controls FXIIIa correlated only to the IMT of the common carotid (p =0.01). In primary APS, FXIIIa was strongly associated with IgG aCL and IgG anti-beta2-GPI (p=0.005 for both). These associations were weaker in the aPL group (FXIIIa with IgG aCL, p= 0.02, with IgG anti-beta2-GPI, p=0.04).
  
  
  CONCLUSIONS
  Enhanced FXIII activity may contribute to atherothrombosis in primary APS via increased fibrin/fibrinogen cross-linking. This pathway is not exclusive to primary APS, being present also in thrombotic controls, but the presence of IgG aPL may favor a higher degree of FXIIIa activation in the primary APS group.
authors.affiliation: Academic Department of Rheumatology, Leeds General Infirmary, Leeds, UK. paxmes@aol.com
authors.forename: Paul R J
authors.initials: PR
authors.lastname: Ames
authors.forename: Luigi
authors.initials: L
authors.lastname: Iannaccone
authors.forename: Jose Delgado
authors.initials: JD
authors.lastname: Alves
authors.forename: Annamaria
authors.initials: A
authors.lastname: Margarita
authors.forename: Luis R
authors.initials: LR
authors.lastname: Lopez
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Brancaccio
mesh_terms: D000328:Adult; D017153:Antibodies, Anticardiolipin / Q000378:metabolism; D016736:Antiphospholipid Syndrome / Q000150:complications / Q000378:metabolism* / Q000473:pathology; D001161:Arteriosclerosis / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D043303:Aryldialkylphosphatase / Q000097:blood; D002339:Carotid Arteries / Q000000981:diagnostic imaging / Q000473:pathology; D003430:Cross-Sectional Studies; D026122:Factor XIIIa / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D019851:Thrombophilia / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D013927:Thrombosis / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D017539:Tunica Intima / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D017540:Tunica Media / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D014463:Ultrasonography
chemical_list: D017153:Antibodies, Anticardiolipin; D026122:Factor XIIIa; D043303:Aryldialkylphosphatase