Rheumatoid factor originally demonstrated in sera from patients with rheumatoid arthritis is now known to be present in many other conditions. Among these are leprosy, hepatic disorders, connective-tissue diseases, subacute bacterial endocarditis, sarcoidosis, and syphilis. (Communications by Vaughn1 and Singer2 are general reviews.) Rheumatoid factor has also been found in a small percentage of normal, healthy populations and in a high percentage of residents of homes for the aged.3 As a consequence, there has been increasing interest in recent years in surveying various other populations (eg, ethnic, occupational, and disease) for the presence of rheumatoid factor.
In many of these investigations, the latex fixation test of Singer and Plotz,4 or some variation of it, has been used for rheumatoid factor detection. However for studying large groups of patients, the majority of who would show negative results, this test may be tedious and time consuming. In an