Elevation of FVIII : C in venous thromboembolism is persistent and independent of the acute phase response

Recent literature has suggested a role for elevated FVIII:C in venous throm boembolic disease (VTED). However since FVIII:C is known to rise in respons e to an acute phase reaction, it is difficult to determine whether the incr eased FVIII:C precedes the thrombosis or represents a secondary reactive ph enomenon. In an attempt to address this question, we followed 35 patients w ith confirmed VTED, raised FVIII:C level (>1.5 iu/ml) and no other thrombot ic tendency. Serial measurements of FVIII:C, vWF:Ag, C-reactive protein and fibrinogen were performed. We hypothesized that a persistent increase in F VIII:C in the absence of any other measures of ongoing acute phase response , would support the idea that elevation of FVIII:C is a constitutional phen omenon. Of this initial group, 94% continued to have an elevated FVIII:C level thro ughout the period of follow up (median 8 months; range 3 to 39 months), wit h no significant difference between the FVIII:C levels determined at first estimation and those obtained during follow up (p = 0.58). Conversely, only 18% had evidence of an acute phase reaction when first assessed, and nonpa rametric ranking analysis demonstrated no correlation between FVIII:C and e ither C-reactive protein or fibrinogen (p = 0.315 and 0.425 respectively). We conclude that increased FVIII:C levels following VTED are persistent, in dependent of the acute phase reaction, and thus may represent a constitutio nal risk factor for VTED.