Reichert LJM, Koene RAP, Wetzels JFM
Urinary excretion of beta-2-microglobulin predicts renal outcome in patients with idiopathic membranous nephropathy

J Am Soc Nephrol (Dec) 6:1666-1669 1995

It would be useful to know in advance which patients with membranous nephropathy will develop progressive renal insufficiency and might therefore benefit from cytotoxic drug therapy. Previously employed predictors include level of proteinuria, renal function, and gender. Histologically, interstitial fibrosis correlates with disease progression. The investigators hypothesized that a marker for impaired tubular function would be an early and sensitive marker for poor prognosis. B2-microglobulin is filtered and then metabolized by the proximal tubule. Impaired proximal tubule function results in increased B2-microglobulin excretion. Patients with membranous nephropathy had B2-microglobulin excretion measured and were observed for changes in renal function.

Retrospective analysis suggested that B2-microglobulin excretion greater than 500 ng/min (in patients with initially normal GFR and proteinuria greater than 3.5 g/24 h) was a valuable marker for poor prognosis. 11/14 of patients with excretion greater than 500 ng/min, but only 2/16 patients with B2-microglobulin excretion less than 500 ng/min doubled their creatinine during approximately 4 years of observation.

Comment: If this observation holds up during prospective observation of a much larger group of patients with membranous nephropathy, it could become a useful clinical tool. It will also be important to use regression analysis to ascertain whether B2-microglobulin excretion is a better prognostic feature than those variables previously identified. (Paller)

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Proteinuria/Hematuria : Membranous GN