Korean J Lab Med.  2008 Dec;28(6):457-464. 10.3343/kjlm.2008.28.6.457.

Diagnostic Utility of AxSYM Anti-Cyclic Citrullinated Peptide Antibody Assay

• Kim KE
• Kim KH
• Woo KS
• Han JY
• Kim JM
• Lee SW
• Chung WT

• KMID: 1781581
• DOI: http://doi.org/10.3343/kjlm.2008.28.6.457

Abstract

BACKGROUND
The presence of rheumatoid factor (RF) is one of the classification criteria of the American College of Rheumatology (ACR) for rheumatoid arthritis (RA), but it has a limitation of low specificity. We compared the diagnostic utility of anti-cyclic citrullinated peptide (CCP) antibodies analyzed by an automated immunoassay system with that measured by a 96 well plate ELISA method. METHODS: The RF and anti-CCP antibodies were determined in 172 serum samples: 52 RA patients, 73 disease controls (systemic lupus, Sjogren's syndrome, palindromic rheumatism), and 47 healthy controls. Anti-CCP antibodies were measured by DIASTAT 96 well plate ELISA method (Axis-Shield Diagnostics, UK) and AxSYM automated microparticle enzyme immunoassay system (Abbott Laboratories, USA). RF was assayed by latex immunoturbidimetry (Toshiba 200 FR, Japan). The diagnostic performances of these tests were compared using a ROC curve analysis, and linearity and precision analysis of AxSYM anti-CCP was carried out. RESULTS: The sensitivities of RF, DIASTAT anti-CCP, and AxSYM anti-CCP were 78.8%, 84.6%, and 82.7%, respectively and the specificities were 72.5%, 88.3%, and 88.3%, respectively. On ROC curve analysis, the area under the curve was 0.924 for AxSYM anti-CCP, 0.886 for DIASTAT anti-CCP, and 0.847 for RF. AxSYM anti-CCP showed a good linearity, and within-run and total-run precision. CONCLUSIONS: Diagnostic performance of automated AxSYM anti-CCP assay was comparable to that of DIASTAT 96 well plate ELISA method. AxSYM anti-CCP assay has an advantage of random access capability and will be useful in laboratories with low sample number and/or with a need of rapid turnaround time.

Keyword

Anti-cyclic citrullinated peptide antibody; Rheumatoid factor; Rheumatoid arthritis; AxSYM immunoassay

MeSH Terms

Adolescent
Adult
Aged
Arthritis, Rheumatoid/*diagnosis
Autoantibodies/*blood
Enzyme-Linked Immunosorbent Assay
Female
Humans
*Immunoenzyme Techniques
Male
Middle Aged
Peptides, Cyclic/*immunology
ROC Curve
Reagent Kits, Diagnostic
Rheumatoid Factor/blood
Sensitivity and Specificity

Figure

• 

  Fig. 1. Distribution of the test results according to the concentrations of anti-CCP antibodies and RF for different groups of patients. Line: cut-off values ([A] DIASTAT, 5 U/mL; [B] AxSYM, 5 U/mL; [C] RF, 18 IU/mL).

• 

  Fig. 2. The receiver operator characteristics (ROC) curves of Dia-STAT anti-CCP (AUC, 0.888), AxSYM anti-CCP (AUC, 0.923) and RF (AUC, 0.847) in RA patients and control group. There was no significant difference among the AUCs.

• 

  Fig. 3. Linearity of AxSYM anti-CCP antibody test. Abbreviation: CCP, cyclic citrullinated peptide.

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