Classifying patients with anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) based on organ involvement at the time patients are first examined has stronger correlation with survival rates, than the customary classification based on disease phenotype, a study has found.
The study, “Long-term patient survival in a Swedish population-based cohort of patients with ANCA-associated vasculitis,” was published in the journal Rheumatic and Musculoskeletal Diseases.
AAV is usually classified, based on phenotype, as a group of diseases consisting of granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA).
The disease is characterized by small vessel inflammation and the presence of auto-antibodies, such as anti-proteinase 3 (PR3), and mainly affects the kidneys, lungs, ear-nose-throat, and skin.
Patients with AAV have a higher mortality rate than the general population, with 80 percent dying within the first year if untreated. And even with treatment using immunosuppressive drugs, the rate of mortality is still higher than that in the general population.
Recent evidence from clinical trials suggests that grouping patients according to clinical similarities, rather than the classical GPA, MPA, and EGPA classification, results in a stronger correlation with survival rates.
This so-called cluster affiliation was used by researchers at Lund University in Sweden to assess survival rates of patients in ordinary practice.
The researchers used data from 195 Swedish AAV patients who had been diagnosed between 1997 and 2010. Patients were classified into five clusters based on organ involvement: gastrointestinal, cardiovascular, non-renal, renal with PR3, and renal without PR3.
Patients were followed up for a period ranging from 2.3 to 18 years (median 11 years). Survival rates were 87 percent, 82 percent, 70 percent, and 55 percent within 1, 2, 5, and 10 years, respectively, with the main causes of death being active vasculitis and infection. Overall, there were 98 deaths compared to 40 deaths expected in the general population, which is consistent with previous findings.
When researchers considered the effect of cluster classification on the death rate they found that, unlike the other clusters, patients within the non-renal cluster did not have a higher death rate compared to the general population. Patients within the gastrointestinal cluster had the highest death rates.
Consequently, the findings of the study emphasize “the suggestion that AAV can be seen as a phenotypic continuum,” the team wrote. They conclude that “this study validates and strengthens the proposed cluster affiliation as an additional tool in assessing the long-term outcome for patients with AAV, demonstrating that the initial clinical presentation might be a more important predictor for survival than diagnosis and type of ANCA.”