Circulating neutrophil gelatinase-associated lipocalin: a useful biomarker for assessing disease activity of ANCA-associated vasculitis.

OBJECTIVES: Biomarkers for assessing disease activity of patients with anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) are important in identifying relapse and guiding treatment. ANCA-induced neutrophil activation and degranulation played an important role in the pathogenesis of AAV and neutrophil gelatinase-associated lipocalin (NGAL) is a biomarker of neutrophil degranulation. The purpose of the current study is to investigate whether NGAL is a useful biomarker for assessing disease activity of patients with AAV.

METHODS: Sequential sera from 19 patients with AAV at initial onset, remission and relapse were collected. Serum NGAL was detected using commercial ELISA kits. The association between serum NGAL and the Birmingham Vasculitis Activity Score (BVAS), ESR, CRP as well as serum ANCA was further investigated.

RESULTS: The 19 patients had 19 relapses. The levels of serum NGAL in patients at initial onset and relapse were both significantly higher than that at remission (285.5 +/- 65.5 ng/ml vs 96.7 +/- 22.2 ng/ml, P < 0.05; 430.3 +/- 98.7 ng/ml vs 96.7 +/- 22.2 ng/ml, P < 0.05, respectively). It was still the case after adjusting for renal function. The levels of serum NGAL closely correlated with BVAS as well as the level of ESR, CRP and ANCA. Moreover, serum NGAL level had a closer correlation with BVAS than ESR, CRP and ANCA did.

CONCLUSION: Circulating NGAL could be used as a useful biomarker for assessing disease activity of patients with AAV.