Background/Purpose: Antineutrophil cytoplasmic antibody (ANCA) negative granulomatosis with polyangiitis (GPA) is a challenging diagnosis. There is paucity of literature regarding the clinical course of ANCA-negative GPA especially when comparing that of ANCA-positive GPA.

Methods: We conducted a single-center, sex and age matched case-control and case-crossover study of ANCA-negative GPA vs. ANCA-positive GPA patients evaluated at our institution from January 1, 1996 to December 31, 2015. Clinical features, outcomes and correlation with ANCA status were characterized.

Results: We identified 110 patients with ANCA-negative GPA, mostly females (72, 65.5%) with median age of 55 (IQR 39-65) years at the time of diagnosis. Disease severity was milder in ANCA-negative GPA (BVAS/WG = 1 vs. 6 points, p< 0.0001). Mucous membranous/eye manifestations were more frequent in ANCA-negative GPA, whereas general symptoms (fever, weight loss, arthralgia, myalgia), pulmonary and renal involvement were more frequent in ANCA-positive GPA. Time to remission was longer in ANCA-negative GPA (27.7 vs. 18.8 months, p=0.004). Greater number of ANCA-positive GPA patients relapsed at 60 months (21.8% vs. 9.1%, p=0.009) compared to ANCA-negative GPA and time to relapse was shorter (49.8 vs. 54.8 months, p=0.043) in ANCA-positive GPA. Patients with general manifestations, BMI > 30 kg/m² and necrotizing granulomatous inflammation were more likely to relapse. ANCA seroconversion from negative to positive was observed in 16 patients. After seroconversion, patients had higher mean BVAS/WG score (p< 0.0001) and increased incidence of relapses (p=0.004) in comparison with the time before ANCA seroconversion. Necrotizing granulomatous inflammation and vasculitis on biopsy at the time of ANCA-negative GPA diagnosis were identified as risk factors for ANCA-positive seroconversion.

Conclusion: ANCA-negative GPA patients have milder disease (BVAS/WG) and are less likely to relapse when compared with patients with ANCA-positive GPA. ANCA seroconversion portends higher disease severity and an increased frequency of relapse.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/negative-vs-positive-antineutrophil-cytoplasmic-antibody-granulomatosis-with-polyangiitis-a-case-control-study/