Immunochemical determination of human immunoglobulins with a centrifugal analyzer

We used an unmodified centrifugal analyzer (Aminco "Roto-Chem II") to measure human immunoglobulins IgG, IgA, and IgM in diluted sera, with diluted commercial monospecific antisera. Turbidimetric endpoint readings at 340 nm were taken at 4 min for IgG and 12 min for IgA and IgM, although multiple timed-interval readings were printed so that the kinetics of the reaction could be observed. Polyethylene glycol was used to enhance the antigen--antibody reaction. A wide range of concentrations can be measured: for IgG, 0.1--24 g/liter; for IgA and IgM, 50--4000 mg/liter. Correlation with radial immunodiffusion and automated immunoprecipitin techniques was satisfactory. Precision, accuracy, linearity, and sensitivity were quite acceptable. Day-to-day precision ranged from 2.5% to 5.2%, depending on sample concentration. The technique is more precise than radial immunodiffusion, and is rapid, simple, and reliable.