Background/Purpose: Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of systemic vasculitides associated with ANCA specific for myeloperoxidase (MPO) or proteinase-3 (PR3), and includes microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA), and eosinophilic granulomatosis with polyangiitis (EGPA). A high prevalence of venous thromboembolism has been reported in several cohort studies of patients with AAV, not only during active disease but also when patients are in remission. Recently, it has also been suggested that patients with AAV in the active stage are in a hypercoagulable state. However, the clinical significance of the increased incidence of venous thromboembolism among patients with AAV has not been fully recognized. Here we examined the relationship between markers for hypercoagulability and disease activity including inflammatory markers and kidney functions, and assessed the implication of abnormal coagulation status in patients with AAV.

Methods: Fifty-five patients who had been referred to Niigata University Hospital and diagnosed as having AAV (MPA (n=29), GPA (n=23), EGPA (n=3)) between 2009 and 2015 were recruited. Plasma fibrin degradation products (FDP), D-dimer, and activated thromboplastin time (APTT) were measured, and the APTT ratio was calculated and standardized using data from control plasma. Disease activity was assessed at the same time in accordance with the Birmingham Vasculitis Activity Score (BVAS). Other laboratory data including kidney function parameters and serum C-reactive protein (CRP) were also examined, and analyzed using Spearman’s rank correlation coefficient and stepwise multiple regression analysis to determine their relationship with coagulation parameters. A P value of <0.05 was taken to denote statistical significance.

Results: The mean value of FDP was elevated at 11.4 μg/ml (normal <9μg/ml), the mean D-dimer value was also elevated at 4.5 μg/ml (normal <1 μg/ml), and the mean APTT ratio was 1.15. In 44 patients, the APTT ratio was >1.01. Spearman’s rank correlation coefficient analysis showed that FDP and D-dimer were positively associated with CRP, daily urinary protein excretion, and BVAS, and negatively correlated with the estimated glomerular filtration rate (eGFR), whereas the APTT ratio was positively associated with BVAS. Although stepwise multiple regression analysis revealed no factor that significantly affected FDP or D-dimer, BVAS was selected as a positive independent variable affecting the APTT ratio (rho=0.3401, p=0.01186). In addition, the mean BVAS was significantly higher in patients with an APTT ratio of ≥1.01 (n=44), compared to patients with an APTT ratio of ≤1.0 (n=11) (16.1 ± 5.4 versus 11.2±5.9, p=0.0114).

Conclusion: Prolongation of APTT reflects AAV disease activity and is considered to be a possible biomarker in affected patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/activated-partial-thromboplastin-time-reflects-disease-activity-in-patients-with-anti-neutrophil-cytoplasmic-antibody-associated-vasculitis/