A More Specific Method for Detecting and Quantitating Rheumatoid Factors Using a Simple Modification of the Ra-Test

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Abstract
Attention is called to the fact that normal human serums contain a hear-labile antiglobulin capable of causing false positive agglutination reactions in the rheumatoid arthritis (RA)-Test of Hyland Laboratories. The development of a simple, but more specific, test is described and a quantitative test for routine use in clinical laboratories is outlined. The greater specificity and sensitivity of this test is owing primarily to incubating the serums at 56 C for 30 minutes prior to testing. This treatment increases the specificity and sensitivity of the test by inactivating the antiglobulin, which is responsible for false positive reactions, as well as the heat-labile inhibitors, which cause false negative results by masking rheumatoid factor activity.