A preliminary immunologic study of urinary proteins: the questionable value of protein clearances in kidney disease.

The clearances of seven different proteins were measured by a quantitative immunodiffusion technique in 15 patients with proteinuria. All urines were also studied by immunoelectrophoresis.The renal histology was evaluated in each case, and no correlation was found between histologic changes and the urinary protein excretion. This observation was confirmed by both immunodiffusion and immunoelectrophoretic techniques. No specific urinary protein excretion pattern was found in six patients with systemic lupus erythematosus.High-molecular-weight proteins were rarely found in urine, even when the glomerular basement membrane was definitely thickened. Low-molecular-weight proteins were often observed, but their clearances were variable. The results do not support the suggestion that protein clearances are valuable diagnostic and prognostic tools in renal diseases. They also do not support the view that glomerular filtration is the sole factor responsible for the final patterns of urinary proteins; tubular reabsorption is probably another important factor.