Latex Immunoassay of Urinary Albumin

A new non isotopic immunoassay based on latex particle agglutination has been developed for the determination of albumin in urine. The assay consists in incubating the urine sample for 30 min at 37 degrees C with latex particles coated with a specific antibody, followed by quantification of the resulting agglutination by particle counting or turbidimetry. The stability of antibody-coated particles during incubation is achieved by diluting them just before the assay in a buffer containing bovine serum albumin. The pH of this buffer, the antibody loading and the concentration of latex particles in the incubation mixture were optimized to obtain the maximal specific and minimal nonspecific agglutination. The albumin standard curve ranges from 25 to 800 micrograms/l. Reproducibility tests performed within and between run gave CV's ranging from 8.2 to 11.6%. The recovery of albumin added to 10 urines averaged 95.5%. A correlation coefficient of 0.96 was obtained between latex immunoassay and nephelometry for the determination of albumin in 51 urines.