Serum IgM rheumatoid factor by enzyme-linked immunosorbent assay (ELISA) delineates a subset of patients with deforming joint disease in seronegative juvenile rheumatoid arthritis

A commercially available indirect enzyme-linked immunosorbent assay for measuring bovine respiratory syncytial virus (BRSV)-specific IgG was adapted to measure virus-specific IgM. Using this assay, the development of rapid IgM responses in experimentally infected calves was observed 7–9 days postinfection, with peak absorbance values ranging from 1.698 to 2.873. When absorbance values were expressed as a percentage of a positive reference serum, a positive/negative threshold of 22% was determined by testing serum samples from 59 healthy 3–5-month-old calves. Acute and convalescent serum samples collected from 151 calves during 38 outbreaks of respiratory disease were tested, and 130 sera were positive. To determine the number of false-positive results due to the presence of IgM rheumatoid factor, a method for depleting serum IgG by pretreatment of sera with a suspension of protein-G-agarose was developed. All sera that initially tested IgM positive were retested following depletion of serum IgG. False-positive IgM reactions were detected in 23 sera (17.7%). Specific IgM responses were confirmed in 107 sera from 84 calves. Evidence of BRSV infection was detected in 34 of 38 outbreaks. In contrast, seroconversion was detected in 69 calves from 24 outbreaks, confirming the diagnostic potential of the IgM assay. Overall correlation between IgM and seroconversion results was 74.2%. Intra- and interassay reproducibility were 12.50% and 17.48%, respectively (mean coefficients of variation).

Download Full-text

Natural killer (NK) cells at inflammatory sites of patients with rheumatoid arthritis and IgM rheumatoid factor positive polyarticular juvenile rheumatoid arthritis

Clinical Rheumatology ◽

10.1007/bf02201027 ◽

1987 ◽

Vol 6 (2) ◽

pp. 215-225 ◽

Cited By ~ 12

Author(s):

J. Thoen ◽

K. Waalen ◽

Ø. Førre

Keyword(s):

Rheumatoid Arthritis ◽

Nk Cells ◽

Rheumatoid Factor ◽

Natural Killer ◽

Juvenile Rheumatoid Arthritis ◽

Igm Rheumatoid Factor

Download Full-text

Measuring rheumatoid factor in nonrheumatoid subjects: immunoturbidimetric assay, latex slide test, and enzyme-linked immunosorbent assay compared

Clinical Chemistry ◽

10.1093/clinchem/37.10.1766 ◽

1991 ◽

Vol 37 (10) ◽

pp. 1766-1769 ◽

Cited By ~ 6

Author(s):

K Ailus ◽

L Melamies ◽

T Tuomi ◽

T Palosuo ◽

K Aho

Keyword(s):

Rheumatoid Arthritis ◽

Pregnant Women ◽

Rheumatoid Factor ◽

Immunosorbent Assay ◽

Fixation Test ◽

Enzyme Linked Immunosorbent Assay ◽

Serum Samples ◽

Weak Reaction ◽

Slide Test

Abstract 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.

Download Full-text