Automated rheumatoid factor assay in a population of patients with rheumatic disease

Rheumatoid factor has been measured in 128 patients having rheumatic disease to compare the Singer-Plotz assay with an automated particle size assay. Correlation coefficient between the two methods using regression analysis revealed r = 0.89, P less than 0.00001 when two different commercial sources of sensitized latex particles were used. Thus rheumatoid factor may be quantitated electronically and represented in arbitrary units (MPRF) without altering clinical interpretation. This methodology may be applicable to many other immunologic assays.