Comparative evaluation of an automated kinetic laser nephelometer with other immunoprecipitin technics for the assay of serum immunoglobulins.

A comparative evaluation of a laser nephelometer (J.T. Baker Immunology Series 420 Laser Nephelometer) with other immunoprecipitin methods in each of two separate laboratories is reported. This is a batch-oriented almost fully-automated laser nephelometer capable of both kinetic and end-point nephelometry. In the kinetic mode, it will automatically detect antigen-excess and perform multiple reassays of further dilutions of sample in a completely unattended mode. Both instrument maintenance and down-time were minimal in both laboratories. The data derived from manufacturer's kits for the assay of IgG, IgA, and IgM were compared to both commercial radial-immunodiffusion and a two-point fixed interval immunoturbidimetric method on a centrifugal fast analyzer. Correlation coefficients exceeded 0.9 in all instances, with variable bias depending on the assay. The apparent bias was felt to be due to a combination of factors including different antibody sources, variance in reference material, assay conditions, difference in measurement modality, and form of mathematical evaluation. The instrument was easy to operate, rapidly gained technologist acceptance, replicated various assay levels at coefficient of variations of less than 10% (between run) and fulfilled our expectations regarding the automatic detection of antigen excess and unattended sample reassay.