A simplified enzyme-linked immunosorbent assay for urinary albumin

A sensitive and simplified competitive binding enzyme linked immunosorbent assay (ELISA) has been developed for quantification of urinary albumin. It was found that, probably because of a high antibody dilution, a conventional ELISA with three incubation steps could be simplified to an assay with only one incubation step without losing sensitivity or precision. The technical conditions of the assay are described. Albumin was coated to the walls of polystyrene microtitre plates. Diluted urine was mixed with rabbit antiserum against albumin and then with alkaline phosphatase conjugated anti-rabbit immunoglobulins. The mixture was then incubated in the microtitre plate for 3 h. After washing the plate, substrate was added and the enzyme activity was measured. Detection limit of the assay was 15 micrograms/l or 1.5 ng. The intra-assay and inter-assay coefficients of variation were 6 and 9%, respectively. The range of 24-h excretion of urinary albumin in apparently healthy subjects was 0.6-27.2 mg.