The avidity of PR3-ANCA in patients with granulomatosis with polyangiitis during follow-up

Abstract

SummaryThe objective of this study is to investigate whether the avidity of proteinase-3-anti-neutrophil cytoplasmic antibody (PR3-ANCA) changes during follow-up in different subgroups of patients with granulomatosis with polyangiitis (GPA). We selected 10 patients with renal relapsing GPA, 10 patients with renal non-relapsing GPA and 10 patients with non-renal relapsing GPA. In all patients, an ANCA rise occurred during remission. The avidity was measured using a chaotropic approach at the time of an ANCA rise and at the time of a relapse in relapsing patients or timematched during remission in non-relapsing patients. No difference was observed in the avidity at the ANCA rise between renal relapsing patients [26Á2% (15Á5-47Á5)], renal patients without a relapse [39Á6% (21Á2-63Á4)] and non-renal relapsing patients [34Á2% (21Á6-59Á5)]. In renal relapsing patients, the avidity increased significantly from the moment of the ANCA rise to the relapse [difference 6Á4% (0Á0-17Á1), P 5 0Á0273]. The avidity did not increase after an ANCA rise in renal non-relapsing patients [difference 3Á5 (26Á0 to 10Á1), P 5 0Á6250] or in non-renal relapsing patients [difference 23Á1% (28Á0 to 5Á0), P 5 0Á5703]. The avidity of PR3-ANCA increases after an ANCA rise during follow-up in renal relapsing patients, but not after an ANCA rise in renal patients who remain in remission or in non-renal relapsing patients.

Birmingham vasculitis activity score of more than 9.5 at diagnosis is an independent predictor of refractory disease in granulomatosis with polyangiitis

“…One study asserted that PR3‐ANCA positivity, but not GPA itself, might be independently associated with the relapse rate of GPA . Another study insisted that the increased titer of PR3‐ANCA might be closely associated with renal relapse, but not non‐renal relapse; a sub‐group analytic study presented a different view that the risk of relapse was associated with the type of AAV, but not the type of ANCA . In addition, ethnic difference could also contribute to the discrepancy of factors affecting relapse rate of GPA between our study and previous studies.…”

Revised 2017 international consensus on testing of ANCAs in granulomatosis with polyangiitis and microscopic polyangiitis

“…This caveat holds true for patient sera, as well as for the reference antibody preparations. Antibodies differ in terms of their IgG subclass composition as well as the avidity, glycosylation and epitope specificity of the antibodies [65][66][67][68][69][70][71][72][73][74] . In particular, epitope specificity might affect standardization of different assay formats, as the accessibility of epitopes might differ between different assay formats.…”

Maintaining remission in patients with granulomatosis with polyangiitis or microscopic polyangiitis: the role of ANCA

“…It should be further investigated why some ANCA rises are directly followed by a relapse while other ANCA rises are not. The pathogenicity of an ANCA rise may be determined by other qualities of the autoantibody, such as the avidity, glycosylation profile, or epitope specificity [96][97][98][99]. The severity of the included cohort and/or relapses is preceded by a tilde if the exact proportion was not described in the article, but an indication could be derived (from organ involvement for example).…”

“…urinary soluble CD163 in active renal vasculitis [110]). Obvious targets to study more intensively concerning ANCA as a predictor of relapse are the avidity, glycosylation profile, or epitope specificity of ANCA [96][97][98][99]. In addition, biomarkers that are not (necessarily) related to ANCA may also be relevant, such as markers reflecting inflammation, injury, and repair [111].…”