EL-RF/3™ (IgM, IgG, IgA) is used for the simultaneous detection and measurement of 3 different isotypes of rheumatoid factors (RF) using directed rabbit IgG as antigen. Depending on the isotypes, the sensitivity is as high as 90% and the specificity 96%. The test is formatted as a panel for efficient multiplex testing for all 3 isotypes.