Why the study?
IgM RF and ACPAs at 3 × UNL are weighted equally in the ACR/EULAR 2010 criteria for rheumatoid arthritis, but their positive predictive values needed determination.
Does the positive predictive value of ACPAs differ from IgM RF at 3 × upper normal limit for diagnosing rheumatoid arthritis?
Does the positive predictive value of ACPAs differ from IgM RF at 3 × upper normal limit for diagnosing rheumatoid arthritis?
ACPAs have a substantially higher positive predictive value for rheumatoid arthritis than IgM RF at 3 × UNL, challenging their equal weighting in the ACR/EULAR 2010 classification criteria.
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ACPAs had higher PPV than IgM RF at 3×UNL for RA; challenges equal weighting in 2010 criteria but remains hypothesis-generating.
Objective: In this retrospective population-based register study, we wanted to determine the positive predictive values (PPVs) of immunoglobulin M rheumatoid factor (IgM RF) and anti-citrullinated protein antibodies (ACPAs) at 3 × upper normal limit (UNL), since they are weighted equally in the American College of Rheumatology (ACR)/ European League Against Rheumatism (EULAR) 2010 criteria for rheumatoid arthritis (RA).Methods: Test results, ordering unit, test date, and patient social security number were collected from the Department of Clinical Immunology at Odense University Hospital from 2007 to 2016 and merged with patient diagnosis from the Danish National Patient Registry.Results: The PPV of IgM RF at 3 × UNL was 14%, compared to a PPV of 43% for ACPAs at 3 × UNL.Conclusion: The PPV of ACPAs is higher than the PPV of IgM RF at 3 × UNL. These findings are not reflected in the ACR/EULAR 2010 classification criteria for RA.
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Tenstad et al. (2019) studied this question.
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