Chemiluminescent immunoassay (CLIA) for urinary albumin

A simple chemiluminescent immunoassay (CLIA) for urinary albumin has been developed based on the use of a chemiluminescent acridinium ester-labelled human albumin and a commercially available antiserum. It includes two incubation steps and a second polyethylene glycol-assisted antibody separation. The sensitivity of detection is 0.016 mg/l, the assay working range is 0.1-5 mg/l, and the inter-assay CVs are less than or equal to 15%. Using 10- and 50-fold sample dilutions in assay buffer, a wide working range (1-250 mg/l) is obtained covering normal and pathological conditions. Timed overnight urine samples (bed rest conditions) were collected on three consecutive days for each patient. Albumin excretion rate (AER) was 4.7 +/- 2.7 micrograms/min (mean +/- SD), range 1-15.9 micrograms/min in 36 healthy subjects (17 male, 19 female, ages 4-56 years), with day-to-day variations of 28.5 +/- 20% (mean +/- SD), range 3.3-76.1%. The use of an acridinium ester as a chemiluminescent (CL) label overcomes the disadvantages of short shelf-life and health and safety hazards associated with radioisotopes. Results compare favourably with those obtained using a commercially available RIA kit.