Nephelometric measurement of ceruloplasmin with a centrifugal analyzer

We describe a rapid nephelometric assay for measurement of ceruloplasmin in serum with the Multistat centrifugal analyzer. In establishing the optimum conditions, the concentration of polyethylene glycol was critical. With a 30 g/L solution of polyethylene glycol, the calibrators and samples react at the same rate, while with a 60/L solution the calibrators react faster than the samples. The reaction rate was not affected by temperatures of 30 or 37 degrees C or pHs between 6.0 and 8.4. There was no interference from bilirubin at a concentration of 180 mg/L, hemoglobin at a concentration of 5000 mg/L, or lipemic serum. The standard curve extends from 50 to 1300 mg/L. Analytical recovery of ceruloplasmin added to four serum specimens averaged 97%. The within-run precision (n = 17) gave CVs of 5.4, 6.1, and 4.0% for samples containing ceruloplasmin at concentrations of 240, 360, and 650 mg/L. Ceruloplasmin concentrations measured by our procedure were compared with those obtained by nephelometric, radial immunodiffusion, and enzymic procedures; the correlation coefficients were 0.93, 0.88, and 0.86.