Clinical factors associated with long-term renal outcomes in Japanese patients with IgA nephropathy presenting with nephrotic range proteinuria: a multicenter, retrospective, cohort study.

BACKGROUND

Patients with IgA nephropathy (IgAN) occasionally present with nephrotic range proteinuria (NRP), but the clinical features and long-term renal prognosis of patients with IgAN-related NRP (IgAN-NRP) with or without nephrotic syndrome (NS) remain elusive.

METHODS

A retrospective, multicenter, cohort study enrolled 788 patients with IgAN from 42 medical centers in 2002-2004. Patients were divided into NRP (group I, n = 39) and non-NRP (group II, n = 749) groups. Group I patients were subdivided into NRP with NS (I-A, n = 14) and NRP without NS (I-B, n = 25) groups. The primary outcome (PO) was a 1.5-fold increase in serum creatinine from baseline. Clinical remission (CR) was defined as both hematuria and proteinuria remission on ≥3 consecutive tests over at least 6 months.

RESULTS

Compared with group II, group I had significantly more severe renal dysfunction and received steroid therapy more frequently. During a median follow-up of 90.0 months, more patients reached the PO in group I (38.5%) than in group II (11.0%). Multivariate analysis of all enrolled patients showed that NRP was a significant independent risk factor for the PO. However, in group I, 10 of 11 patients who achieved CR had a favorable renal prognosis, and corticosteroid therapy significantly attenuated the risk for the PO. When comparing groups I-A and I-B, baseline renal impairment and cumulative probabilities of the PO were comparable.

CONCLUSION

Regardless of the presence of NS, IgAN-NRP is a critical factor leading to a poor prognosis, unless CR is achieved. Intensive treatment might be vital for IgAN-NRP.