ANCA-Positive Patients: The Influence of PR3 and MPO Antibodies on Survival Rate and The Association with Clinical and Laboratory Characteristics.

Objectives: To compare the survival rate, and the clinical and laboratory characteristics in patients, characterized by the presence of certain anti-neutrophil cytoplasmic auto-antibodies (ANCAs).

Methods: In a retrospective observational study, we analyzed the data of all patients with a positive ANCA test between 1995 and 2005 at our hospital. Based on serology patients were divided in three subgroups (ANCA-Proteinase 3 (PR3), ANCA-Myeloperoxidase (MPO) and atypical ANCA), irrespective of the diagnosis. Patient survival was compared by Kaplan Meier survival analysis. Differences in clinical and laboratory characteristics between the groups of specific ANCAs were determined.

Results: Fifty-four ANCA-positive patients were analyzed. Eighteen of these patients were ANCA-PR3-positive, 17 were ANCA-MPO-positive and 19 had a atypical ANCA. A random control group was created of matched ANCA negative patients. Average follow-up time was 52 months. The calculated five year survival rate in respectively the ANCA-PR3- positive group, the ANCA-MPO-positive group, the atypical ANCA group and the ANCA-negative group was 45%, 81%, 90% and 100%. (P = 0.012, Wilcoxon test). A higher mean leukocyte count, a higher mean erythrocyte sedimentation rate and more fever was observed in the ANCA-PR3-positive group compared to the ANCA-MPO-positive group.

Conclusions: A remarkable lower survival rate was observed in ANCA-PR3-positive patients compared to ANCA-MPO-positive patients. We also demonstrated that patients characterized by the presence of a defined ANCA differ in clinical and laboratory characteristics.