Underestimation of serum albumin by the bromcresol purple method and a major endogenous ligand in uremia.

In hemodialyzed patients, the serum albumin concentration determined by the bromcresol purple (BCP) method was lower than that determined by an immunological method. The degree of underestimation appeared to be well correlated to the serum concentration of 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), a major endogenous ligand substance present in uremic serum. CMPF inhibited in vitro the binding of BCP to serum protein and human serum albumin. Our results suggest that CMPF is a major interferent in the underestimation of the serum albumin concentration by the BCP method in uremia.