title: Raising rheumatoid factor cutoff helps distinguish rheumatoid arthritis.
abstract: The presence of rheumatoid factor (RF) is one of the clinical criteria for the diagnosis of rheumatoid arthritis (RA). The cutoff point of RF assays is usually based on a reference level obtained from normal subjects in the same population as the patients. We evaluated 63 rheumatoid arthritis (RA), 25 other arthritis patients and 110 blood donors. Their rheumatoid factors (RF) ranged from < 9.9 to 2,264, < 9.9 to 262, and < 9.9 to 66 mIU/ml, respectively. The sensitivity at different cutoff points of 15, 20, and 25 mIU/ml was 92.1%, 90.5%, and 88.9%, respectively. The specificity at the same cutoff points was 81.5%, 84.4%, and 85.2%, respectively. Having minimally sacrificed the sensitivity, we recommend using a higher RF cutoff to increase specificity.
authors.affiliation: Clinical Immunology Laboratory, Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand.
authors.forename: Daungtawan
authors.initials: D
authors.lastname: Thammanichanond
authors.forename: Mongkol
authors.initials: M
authors.lastname: Kunakorn
authors.forename: Sureewan
authors.initials: S
authors.lastname: Kitiwanwanich
authors.forename: Kalayanee
authors.initials: K
authors.lastname: Attamasirikul
authors.forename: Kanokrat
authors.initials: K
authors.lastname: Nantiruj
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000453:epidemiology / Q000276:immunology*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007155:Immunologic Factors / Q000097:blood; D008297:Male; D008875:Middle Aged; D012217:Rheumatoid Factor / Q000097:blood*; D012680:Sensitivity and Specificity; D013785:Thailand / Q000453:epidemiology
chemical_list: D007155:Immunologic Factors; D012217:Rheumatoid Factor