Measuring rheumatoid factor in nonrheumatoid subjects: immunoturbidimetric assay, latex slide test, and enzyme-linked immunosorbent assay compared.
Previous studies of patients with rheumatoid arthritis (RA) have shown a good correlation between results from immunoturbidimetric assays of rheumatoid factor (RF) and latex fixation tests. To extend the research to non-RA subjects, we tested sera from 1000 pregnant women, half each in the first and third trimesters. By turbidimetry, 24 non-RA sera were regarded as positive for RF (greater than or equal to 20 int. units/mL) and 18 sera as borderline (15-19 int. units/mL). By the latex fixation test, 28 non-RA sera gave a clear reaction (positive) and 17 sera a weak reaction (borderline). The association between the tests was statistically highly significant (P less than 0.001). All sera with positive and borderline reactions were tested by enzyme-linked immunosorbent assay for RF isotypes, together with a random subsample of about one-sixth of the original serum samples. Positive RF results by immunoturbidimetry were predominantly due to the presence of IgM-RF. In contrast to some earlier findings, we saw no difference in the prevalence of positive RF reactions between sera from the first and third trimesters.
Department of Immunobiology, National Public Health Institute, Helsinki, Finland.
K
K
Ailus
L
L
Melamies
T
T
Tuomi
T
T
Palosuo
K
K
Aho
D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007841:Latex Fixation Tests; D009391:Nephelometry and Turbidimetry; D011247:Pregnancy; D012217:Rheumatoid Factor / Q000097:blood*
D012217:Rheumatoid Factor