Introduction
Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis
comprises a heterogeneous group of vasculitides characterised by
inflammation and necrosis of small and medium-sized vessels, usually
associated with autoantibodies directed against neutrophil lysosomal
enzymes (1).
Consensus statements on testing methods, clinical indications and
interpretation of ANCA tests have been published (2). However, the
usefulness of monitoring ANCA levels in the clinical follow-up of AAV is
still a matter of debate. Most studies have focused on analysing the
sensitivity, specificity, and predictive value of an increase in ANCA
levels to predict clinical relapses. The results of these studies vary
widely, probably related to the heterogeneity of the vasculitides
included, the criteria used to define an increase in ANCA titres, and
the criteria used to define a clinical relapse (3). At present, most
clinicians continue to routinely monitor ANCA levels, although several
studies have claimed that there is no need to perform such serial
measurements since they have a low sensitivity and specificity to
predict a clinical relapse (4-7).
Long-term observation of patients with AAV allows the identification of
different patterns of ANCA titers during follow-up. Some patients will
display a monophasic pattern, with an initial peak of antibodies that
later become negative, while others will present persistent low levels,
or recurrent peaks, or will remain with persistently high ANCA levels.
The present study aimed to characterise these longitudinal patterns and
to determine their clinical assocations and possible prognostic impact.