Anaemia is an essential complication of ANCA-associated renal vasculitis: a single center cohort study

BACKGROUND: Anaemia is a common complication of patients with antineutrophil cytoplasmic antibody (ANCA)-associated renal vasculitis. Nevertheless, the cause and degree of such cases of anaemia have not been elucidated in detail. We aimed to investigate the prevalence, cause, pathogenesis of anaemia and the impact of anaemia on prognosis in patients with ANCA-associated renal vasculitis. METHODS: We identified 45 patients with ANCA-associated renal vasculitis that were clinically and/or histologically diagnosed and treated from 2003 to 2014 at University of Tsukuba Hospital. The relationships between anaemia and various clinicopathological findings were evaluated. RESULTS: At the time of diagnosis of ANCA-associated renal vasculitis, all patients showed anaemia, with a mean haemoglobin level of 7.5 ± 1.3 g/dL. Renal anaemia was diagnosed in 92% of patients, anaemia of chronic disease (ACD) in 56%, and anaemia due to hemorrhage in 20%. Next, the patients were divided into two groups according to anaemia severity: minimum haemoglobin (min Hb) < 7.5 (n = 24) and min Hb ≥ 7.5 (n = 21). A comparison of baseline characteristics showed that serum albumin, maximum serum creatinine, minimum estimated glomerular filtration rate (eGFR), serum cystatin C, and the area of tubulointerstitial damage were significantly different between the haemoglobin groups (p < 0.05). No significant intergroup differences were observed in iron-related or inflammation-related data. With regard to the relationship between anaemia severity and prognosis, patients in the min Hb < 7.5 group tended to have a lower eGFR. Anaemia severity was associated with markedly lower survival (Log-rank test, p = 0.03). CONCLUSIONS: In this cohort of patients with ANCA-associated renal vasculitis, all subjects exhibited anaemia. In regard to the cause and pathogenesis, the most prevalent form of anaemia was renal anaemia, not ACD, and a potential reason for the high prevalence of anaemia in our cohort may have been the interaction between renal anaemia and ACD. Moreover, anaemia severity was significantly associated with the degree of renal dysfunction and life prognosis.