Urinary fibrin split products in lupus nephritis.

Antigen-antibody interaction and fibrin deposition at the glomerular basement membrane can release activators that ultimately convert fibrin into degradation products of varying molecular size. Thus, increased urinary fibrinogen/fibrin split products (FSP) might be expected in active lupus nephritis. A longitudinal study was done on 27 patients with biopsy-proven lupus nephritis. Those patients who were persistent FSP excretors were found to be at a significantly greater risk of progressive nephritis and renal death than those who were FSP negative. It is suggested that FSP excretion in lupus nephritis, particularly on a continued basis and despite normalization of other renal disease parameters, is a grave prognostic sign.