220. A systematic review and meta-analysis on the value of serial ANCA titer evaluation

Background: ANCA-vasculitis (AAV) patients frequently suffer from relapses and risk subsequent organ damage. There is much debate on the value of serial ANCA titer evaluation to monitor disease activity. We aimed to evaluate the association between ANCA rises and disease flares at (I) moment of the rise, (II) within 6 months or (III) within a year from the rise. Methods: 3 databases (MEDLINE, EMBASE and COCHRANE) were searched from 1993 through 2021. We included studies that reported flare incidence within 12 months after an ANCA rise measured by ELISA in peripheral blood of AAV patients in remission. Quality assessment was performed using QUADAS-2. Finally, a meta-analysis was carried out to estimate average OR using a random effects model. Results: 20 unique studies were included. The methodological quality was limited due to risk of selection bias. An ANCA rise often preceded a disease flare within 6 months (OR 4.45, 95% CI 1.87-10.58) and less often within 12 months (OR 2.88, 95% CI 1.21-6.88), while it was not indicative of a concurrent flare (OR 0.13, 95% CI 0.02-0.18). Once a flare is diagnosed, ANCA is significantly more often present than not (OR 10.80, 95% CI 3.82-30.55). As expected based on clinical variability, there was substantial heterogeneity across studies in all analyses (I2 = 70%-87%). Conclusions: An ANCA measurement upon clinical suspicion of a disease flare aids diagnosis. Patients with a rise in ANCA are at risk of encountering disease flares in the upcoming 6 or 12 months. Disclosures: This work was supported by the Dutch Kidney Foundation [Grant number 19OK007 to MH and YV] and ZonMW [VENI grant number 91617058 to PK