1152: Relation Between Positive MPO-ANCA Antibodies And: Associated Diseases, Anca-associated Vasculitis Specificty, Severity and Prognosis. Study from a Single University Hospital

Fabricio Benavides¹, Monica Renuncio-García¹, Salma Al Fazazi², clara escagedo Cagigas¹, maria rodriguez Vidriales¹, Vanesa Calvo Río³, Juan Irure-Ventura¹, luis martin penagos⁴, Marcos Lopez-Hoyos⁵ and Ricardo Blanco⁶, ¹Hospital Universitario Marqués de Valdecilla, Santander, Spain, ²Hospital Universitario Puerta Del Mar, Cádiz, Spain, ³Valdecilla Hospital, Santander, Spain, ⁴Division of Nephrology, Immunopathology Group, Hospital Universitario Marqués de Valdecilla-DIVAL, Santander, Spain, ⁵Marques de Valdecilla University Hospital-IDIVAL, Santander, Spain, ⁶Hospital Universitario Marqués de Valdecilla, IDIVAL, Santander, Spain

Background/Purpose: ANCA-associated vasculitis (AAV) is a group of pathologies characterized by necrotizing inflammation that mainly affects small and medium-sized vessels. Serum anti-neutrophil cytoplasmic antibodies (ANCA), mainly anti-myeloperoxidase (anti-MPO) and anti-proteinase 3, levels may correlate to severity and prognosis of the disease. Our objective was to identify the diseases associated with positive anti-MPO antibodies detected in a single university hospital and attempt to establish whether there is a cut-off point that correlates anti-MPO antibody levels with disease severity and prognosis.

Methods: Table 1 summarizes the frequency of positive anti-MPO antibodies, using laboratory established cut-off value, in different diseases based on a retrospective investigation of 101 positive anti-MPO antibody patients. Then, anti-MPO specificity to vasculitis was evaluated. Furthermore, data of renal disease (hematuria and/or proteinuria) and pulmonary involvement (hemoptysis, asthma and/or respiratory insufficiency) were collected at vasculitis diagnosis, as well as whether the illness progressed to the stage of requiring dialysis, transplantation, or mortality.

Results: For anti-MPO antibodies with a diagnosis of vasculitis (n=77), an area under the curve (AUC) was calculated (AUC=0.8084), and a cut-off point of 41.5 IU/ml was determined (Figure 1). When the analysis was restricted to exclusively microscopic polyangiitis diagnoses (n=34), the cut-off point was 36.5 IU/ml with an AUC of 0.6435. There were significant differences in anti-MPO levels between patients with renal or pulmonary dysfunction (n=65) versus those without them (n=36) (p=0.0003), and a cut-off threshold of 60 IU/ml was established. Finally, after evaluating the illness's prognosis, an AUC= 0.5546 was found, being no significant differences between those patients who had a worse disease progression (n=19) and those who did not (n=82) (p=0.4643).

Conclusion: Anti-MPO levels at the moment of vasculitis diagnosis are related with disease severity but not with disease outcome.






F. Benavides: None; M. Renuncio-García: None; S. Al Fazazi: None; c. escagedo Cagigas: None; m. rodriguez Vidriales: None; V. Calvo Río: None; J. Irure-Ventura: None; l. martin penagos: None; M. Lopez-Hoyos: None; R. Blanco: AbbVie, 5, 6, Amgen, 6, AstraZeneca, 2, BMS, 6, Eli Lilly, 6, Galapagos, 2, 6, Janssen, 2, 6, MSD, 6, Novartis, 2, 6, Pfizer, 2, 6, Roche, 5, 6, Sanofi, 6.