The temporal relationship between urinary C5b-9 and C3dg and clinical parameters in human membranous nephropathy

We have previously reported that urinary excretion of the complement activation products C3dg and C5b-9 in human membranous nephropathy (MN) correlated with clinical outcome in a cross-sectional analysis. We report here the results of a retrospective longitudinal study of the temporal relationship between urinary C3dg and C5b-9 excretion and clinical parameters. A group of 23 adult patients with biopsy-proven MN were studied over a mean time period per patient of 3.5 years. Freshly voided urine samples were collected regularly; C3dg and C5b-9 were measured by ELISA (mean number of samples per patient = 13). During the period of the study, nine patients with declining renal function (group A) were treated with a standard steroid regimen. Serum creatinine had improved or stabilized in seven of these patients at the end of treatment. All nine patients were excreting C3dg and C5b-9 before treatment. Six other patients with declining renal function (group B) were not treated with steroids because of clinical contraindications. Serum creatinine continued to increase during the study in four of these six patients. C3dg and C5b-9 were present in the urine samples of these six patients on the majority of dates tested. Eight patients maintained stable renal function during the study (group C), either normal (6 patients) or impaired (2 patients). Of these patients, six were consistently negative for urinary C3dg and C5b-9 despite persistent proteinuria, and one patient who was initially positive became negative within 15 months, and remained negative for the rest of the study period. One patient was positive on one of 12 occasions tested. These results suggest that urinary complement activation products indicate ongoing active glomerular damage and may prove to be important determinants for the introduction and monitoring of therapy.