Use of the D-dimer assay for diagnosing thrombosis in cases of canine cutaneous vasculitis

The objectives of this study were to measure D-dimer concentrations and assess their value in diagnosis of thrombosis in three groups of dogs; (i) dogs with cutaneous vasculitis without histopathological evidence of thrombosis; (ii) dogs with cutaneous vasculitis with histopathological evidence of thrombosis; and (iii) pruritic dogs with erythematous skin and underlying allergic skin disease. D-dimer test results were reported as negative at <250 ng/mL, and positive at > or =250 ng/mL. Ten dogs with a diagnosis of atopic dermatitis and/or cutaneous adverse food reaction were enrolled in the study, and the D-dimer results were <250 ng/mL (eight dogs) and 250-500 ng/mL (two dogs). Twenty-six dogs with a diagnosis of cutaneous vasculitis had blood samples submitted for D-dimer analysis at the time of the initial submission of skin biopsies and results were: 15 had cutaneous vessel thrombi present with a D-dimer of >500-1000 ng/mL (14 dogs) and >1000 ng/mL (one dog); 11 dogs had no histological evidence of thrombi with a D-dimer of <250 ng/mL (four dogs), 250-500 ng/mL (three dogs) and >500-1000 ng/mL (four dogs). However, two of four dogs with a D-dimer of >500-1000 ng/mL without histological evidence of thrombi developed necrotic skin lesions over the next 24-48 h. In conclusion, a D-dimer >500 ng/mL is strong evidence to support the current presence or subsequent development of cutaneous vessel thrombosis, and a D-dimer of <500 ng/mL correlates well with the absence of cutaneous vessel thrombi and necrotic skin lesions. No dogs with histopathological evidence of thrombi had a false-negative D-dimer.