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Anti-carbamylated protein antibodies: are they useful for the diagnosis of rheumatoid arthritis?

1, 2, 3, 4, 5, 6, 7

 

  1. Leeds Institute of Rheumatic and Musculoskeletal Medicine, The University of Leeds, UK. mmefp@leeds.ac.uk, f.ponchel@leeds.ac.uk
  2. Department of Rheumatology, Leiden University Medical Centre, Leiden University, The Netherlands.
  3. Leeds Institute of Rheumatic and Musculoskeletal Medicine, The University of Leeds, UK.
  4. Leeds Institute of Rheumatic and Musculoskeletal Medicine, The University of Leeds, UK.
  5. Leeds Institute of Rheumatic and Musculoskeletal Medicine, The University of Leeds, UK.
  6. Department of Rheumatology, Leiden University Medical Centre, Leiden University; and Department of Immunohaematology and Blood Transfusion, Leiden University Medical Centre, The Netherlands.
  7. Leeds Institute of Rheumatic and Musculoskeletal Medicine, The University of Leeds; and NIHR Leeds Musculoskeletal Biomedical Research Centre, The Leeds Trust Teaching Hospital, Leeds, UK.

CER13007
2021 Vol.39, N°1
PI 0146, PF 0150
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PMID: 32662401 [PubMed]

Received: 10/12/2019
Accepted : 30/03/2020
In Press: 30/06/2020
Published: 05/02/2021

Abstract

OBJECTIVES:
ACR/EULAR-2010 classification criteria for rheumatoid arthritis (RA) rely heavily on the presence of anti-citrullinated peptide antibody (ACPA). The role of anti-carbamylated protein antibodies (anti-CarP) in this context is uncertain. We aimed to investigate the value of anti-CarP for RA classification in patients with early inflammatory arthritis.
METHODS:
Patients (n=402) were recruited from an early arthritis clinic and followed for 24 months. Healthy controls (n=95) were included. An anti-CarP ELISA was performed (aU/mL). Statistical analysis used regression and AUC analysis.
RESULTS:
The criteria for RA were met by 195/402 patients at inclusion; 28 developed RA during follow-up and 179 had other diagnosis (non-RA). 97/195 (49%) RA patients were anti-CarP+ (median 250 uA/mL [IQR 25–762]). In the group that progressed to RA, 7/28 (25%) were positive (82 uA/mL [13-235]) compared to non-RA (p=0.001) with 13/179 (7%) positive (26 uA/mL [5-80]). Being anti-CarP+ alone was observed in 17 patients of whom 7 (41%) were RA. Levels/positivity were not associated with other parameters. Anti-CarP+ had an odds ratio (OR) 6.5 for predicting RA (OR=17.1 for ACPA+ and OR=2.5 for RF+). In ACPA- patients, anti-CarP+ was also predictive of RA (OR=2.39). Being ACPA+/anti-CarP+/RF+ had a high predictive value for RA (OR=29.9 sensitivity/specificity (sen/spe) 33%/99%, positive/negative predictive values (ppv/npv) 97%/54%), however, being ACPA+/anti-CarP+ was superior (OR=36.1 sen/spe=41%/99%, ppv/npv=98%/57%) while being ACPA+/RF+ was inferior (OR=11.9, sen/spe=54%/95%, ppv/npv=94%/62%).
CONCLUSIONS:
For RA classification, anti-CarP+ was less sensitive than ACPA, but more specific than RF. Anti-CarP+ may prove useful, classifying early arthritis patients, notably ACPA- patients.

DOI: https://doi.org/10.55563/clinexprheumatol/u891rd

Rheumatology Article