Clinical significance of anti‐citrullinated peptide antibody in Japanese patients with established rheumatoid arthritis

Diagnostic performance of anti-cyclic citrullinated peptide and rheumatoid factor in patients with rheumatoid arthritis

AIM

To compare the diagnostic performance of rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibody (anti-CCP) in the diagnosis of patients with rheumatoid arthritis (RA) in Taiwan.

METHODS

Serum concentrations of RF and anti-CCP were measured in 246 cases, including 39 patients with RA and 207 patients with other rheumatic diseases (non-RA). The age, sex, clinical presentation, RF, anti-CCP results and the final diagnoses were recorded and analyzed. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+) and negative likelihood ratio (LR-) were calculated.

RESULTS

Among all 246 patients, 39 (15.9%) were diagnosed with RA and 207 (84.1%) were diagnosed with other rheumatic diseases (non-RA). In the diagnosis of RA, the sensitivity, specificity, PPV, NPV, LR+ and LR- of the RF test were 67%, 79%, 37%, 93%, 3.12, and 0.42, respectively. The corresponding data for the anti-CCP test were 79%, 98%, 86%, 96%, 32.91 and 0.21, respectively. The presence of either anti-CCP or RF increased the sensitivity to 85%, and when they both were present, the specificity increased to 98%. Among the 39 RA patients, 26 (66.7%) tested positive for RF, and 31 (79.5%) tested positive for anti-CCP. RF was positive in two of eight anti-CCP-negative patients with RA, and anti-CCP was positive in seven of 13 RF-negative patients with RA.

CONCLUSIONS

The RF and anti-CCP tests are complementary, and the co-detection of these antibodies can increase the detection rate and provide important clinical value in the diagnosis of RA. Both anti-CCP and RF positivity are useful for the diagnosis of RA, and use of both tests together improves the diagnostic sensitivity.

Determination of the Subset of Sjögren’s Syndrome with Articular Manifestations by Anticyclic Citrullinated Peptide Antibodies

Objective.

To investigate whether anticyclic citrullinated peptide antibodies (anti-CCP) predict the subset of Japanese patients with Sjögren’s syndrome (SS) with articular manifestations.

Methods.

Eighty-seven patients with SS were enrolled. Prevalence of anti-CCP antibodies, IgM rheumatoid factor, anti-Ro/SSA antibody, anti-La/SSB antibody, and serum IgG concentration and their relation to articular manifestations were examined. Articular manifestations included morning stiffness and the presence of tender or swollen joints.

Results.

Eighty-seven SS patients were divided into 3 groups: 14 secondary SS with nonerosive rheumatoid arthritis (RA); 47 primary SS with articular manifestations; and 26 primary SS without articular manifestations. Ten out of 14 secondary SS with nonerosive RA expressed anti-CCP. Anti-CCP was the only statistically proven marker preferentially distributed in patients with articular manifestations (the first 2 groups) compared to primary SS without such manifestations; however, its frequency was low in primary SS. No patient with primary SS without articular manifestations expressed anti-CCP.

Conclusion.

Anti-CCP is found in the subset of Japanese with SS with articular manifestations although most of those with anti-CCP-positive SS were classified as secondary SS with RA.