Issue: 2009 > February > original article

Urinary excretion of low-molecular-weight proteins as prognostic markers in IgA nephropathy

H.P.E. Peters, J.A.J.G. van den Brand, J.F.M. Wetzels


Background: Immunoglobulin A nephropathy (IgAN)
is characterised by high variability in clinical course and
outcome. Accurate prediction of prognosis is needed
to optimise treatment. Urinary α1-microglobulin and β2-microglobulin are markers of tubulointerstitial injury and predict the risk of end-stage renal disease (ESRD) in idiopathic membranous nephropathy. We questioned the relevance of these markers in IgAN.
Methods: We included patients with biopsy proven
IgAN, who were evaluated for proteinuria in our centre
between 1995 and 2007. Data were analysed using
univariate and multivariate Cox regression for the
outcome variables ESRD and progression (rise in serum
creatinine of >50% or start of immunosuppressive therapy).
Results: Seventy patients (71% men) were selected.
Median age was 39 years, median serum creatinine 140
&#956;mol/l, and median proteinuria 2.4 g/day. Median urinary &#945;1-microglobulin excretion was 23.5 &#956;g/min (range 3.5-275.3) and median urinary &#946;2-microglobulin excretion was 0.4 &#956;g/min (range 0.1-62.1). Both &#945;1m and &#946;2m correlated significantly with serum creatinine (r = 0.65, p<0.01 and r = 0.62, p<0.01) and total proteinuria (r = 0.35, p<0.01 and r = 0.28, p<0.05). During follow-up (median 75 months) 25 patients (36%) developed ESRD, and 46 patients (66%) showed progression. 19 patients (27%) were treated with immunosuppressive agents. In univariate analysis urinary &#945;1- and &#946;2-microglobulin predicted ESRD and progression.
In multivariate analysis only serum creatinine and urinary protein were independent predictors of both outcomes.
Conclusion: Urinary excretion of low molecular weight
proteins did not offer an advantage over total proteinuria
and serum creatinine in predicting prognosis in patients
with IgAN.