Routine quantification of rheumatoid factor by rate nephelometry.

Abstract

SUMMARYIn a cross-sectional study of over 3000 consecutive serum specimens the levels of rheumatoid factor (RF) measured by rate nephelometry (Beckman ICS II) were compared with values obtained by the more traditional methods of sheep cell agglutination (Rose-Waaler) and latex agglutination. Similar values for sensitivity and specificity were found for all three methods for rheumatoid arthritis, with nephelometry giving slightly higher levels of sensitivity for other rheumatic disorders. A significant correlation (r=0-46, p<001) was found between the nephelometric and Rose-Waaler method for 147 consecutive seropositive specimens. Of interest, however, several disparate results were observed, and explanations for these were sought. Longitudinal studies of RF were performed in 49 seropositive patients over a two-year period. The nephelometric method was considered superior compared with the other techniques because of its ability to detect changes in absolute levels at earlier stages and its low interassay coefficient of variance (11%).We

Autoantibodies in Rheumatoid Arthritis – Laboratory and Clinical Perspectives

“…There is often an obvious discrepancy between quantitative results from RF measurements performed with different methods. Already one of the first studies on RF measured with nephelometry noted only a modest correlation between agglutination test titers and nephelometry (r=0.46) after excluding seronegative patients (19). Comparisons between nephelometry and turbidometry have also showed significant differences, especially in the low positive range (76), and even different IgM RF immunoassays have shown clear discrepancies depending on whether the target antigen source was human or rabbit IgG (77).…”

“…tests appeared based on the agglutination of latex-containing particles of uniform size instead of sheep red blood cells (18). Large scale automation was made possible with the development of nephelometric (19,20) and turbidimetric (21) techniques. Until then, all methods had been isotype-nonspecific, although they all, due to assay format, mainly detected IgM RF.…”

Idiopathic Nonspecific Interstitial Pneumonia

“…Serologic studies were performed in a variety of laboratories, including referring clinics/ hospitals and at the study hospital, using standard techniques (23,24). All laboratory tests were ordered as part of clinical evaluation and not performed for the purposes of this study.…”

Transcriptional profiling of leukocytes from rheumatoid arthritis patients before and after anti-tumor necrosis factor therapy: A comparison of anti-nuclear antibody positive and negative subsets

“…RF was assayed by nephelometry (turbidimetry) and reported as IU/ml using a particle-enhanced immunoassay with latex-bound heat inactivated IgG, which was bound by RF antibodies in patient serum to form antigen-antibody complexes. The resulting agglutination reaction was read on a Siemens Advia 1200 System (Siemens Healthcare Diagnostics, Inc., Tarrytown, NY, USA) using methods previously reported in detail ( 25 , 26 ). Values <15 IU/ml were considered to be normal (negative) for RF.…”