Urinary fibrin split products in lupus nephritis. Correlation with other parameters of renal disease

A total of 337 measurements of urinary fibrin(ogen) split products (FDP) have been made over a 2‐year period on 56 patients with lupus nephritis. Nineteen patients were studied during a 14 week controlled trial of cytoxic drug therapy and the remaining patients were studied at random intervals. An attempt was made to correlate FDP excretion levels with accepted parameters of renal disease and of lupus activity. While patients with significant nephritis by other criteria excreted elevated levels of FDP when compared with normal individuals or patients with rheumatoid arthritis, the excretion by individual patients fluctuated markedly in sequential measurements. In addition FDP excretion correlated poorly with BUN, creatinine clearance, and protein excretion, and with indicators of lupus activity (C3 and anti‐DNA levels). We conclude that although fibrin deposition in the glomerulus is almost certainly an important factor in the pathogenesis of lupus nephritis, urinary FDP levels are not helpful in assessing the progress of glomerular damage in individual patients.