Diagnostic Performances of Anti-Cyclic Citrullinated Peptides Antibody and Antifilaggrin Antibody in Korean Patients with Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease of unknown etiology. We studied the diagnostic performances of anti-cyclic citrullinated peptides antibody (anti-CCP) assay and recombinant anti-citrullinated filaggrin antibody (AFA) assay by enzyme linked immunosorbent assay (ELISA) in patients with RA in Korea. Diagnostic performances of the anti-CCP assay and AFA assay were compared with that of rheumatoid factor (RF) latex fixation test. RF, anti-CCP, and AFA assays were performed in 324 RA patients, 251 control patients, and 286 healthy subjects. The optimal cut off values of each assay were determined at the maximal point of area under the curve by receiver-operator characteristics (ROC) curve. Sensitivity (72.8%) and specificity (92.0%) of anti-CCP were better than those of AFA (70.3%, 70.5%), respectively. The diagnostic performance of RF showed a sensitivity of 80.6% and a specificity of 78.5%. Anti-CCP and AFA showed positivity in 23.8% and 17.3% of seronegative RA patients, respectively. In conclusion, we consider that anti-CCP could be very useful serological assay for the diagnosis of RA, because anti-CCP revealed higher diagnostic specificity than RF and AFA at the optimal cut off values and could be performed by easy, convenient ELISA method.

Diagnostic Performance of the Antifilaggrin Antibody in Rheumatoid Arthritis / 임상검사와정도관리

BACKGROUNDS: Rheumatoid factor (RF) is common serological marker for the diagnosis of rheumatoid arthritis (RA), but its sensitivity and specificity are not satisfactory for the diagnosis of RA. Therefore, we investigated the diagnostic performance of a new antifilaggrin antibody test by enzyme linked immunosorbent assay (ELISA) in RA. METHODS: Recombinant human filaggrin was deiminated in vitro by peptidylarginine deiminase and used as the coating antigen for ELISA. We performed the RF and the antifilaggrin antibody for 324 RA patients, 251 non-RA patients (rheumatic diseases other than RA), and 286 normal individuals and evaluated the sensitivities and specificities of RF and antifilaggrin antibody. Optimal cut off values were calculated as mean+2SD in 95% confidence interval except 3SD for 286 normal individuals. Optimal cut off values of antifilaggrin antibody and RF were 9.6 U/ml and 12 U/ml, respectively. RESULTS: The sensitivities and specificities of antifilaggrin antibody were 44.8% and 89.2% at optimal cut off values. The sensitivity and specificity of RF were 75.0% and 83.3%. Combination of "antifilaggrin antibody and RF" showed significantly high specificity of 95.2% and that of "antifilaggrin antibody or RF" showed slightly high sensitivity of 79.3% at optimal cut off values. Antifilaggrin antibody was positive in 17.3% among 81 sero-negative RA patients. CONCLUSION: We considered that antifilaggrin antibody could be used a supplementary test of RF for the diagnosis of RA, because "antifilaggrin antibody and RF" had higher diagnostic specificity than RF alone and antifilaggrin antibody test was easy, convenient ELISA method in performance.

Diagnostic Performance of the Anti-Cyclic Citrullinated Peptide Antibodies in Rheumatoid Arthritis / 대한진단검사의학회지

BACKGROUND: The Rheumatoid Factor (RF) is the only serological marker in the diagnosis of rheumatoid arthritis (RA), but its sensitivity and specificity are not satisfactory for the diagnosis of RA. Therefore, we investigated the diagnostic performance of a new anti-cyclic citrullinated peptide antibodies test (anti-CCP) by the enzyme-linked immunosorbent assay (ELISA) in RA. METHODS: A cyclic peptide variant that contains citrulline was used as an antigenic substrate in ELISA. We performed the RF and anti-CCP in 324 RA patients, 251 non-RA patients (rheumatic diseases other than RA), and 286 normal individuals. Diagnostic performances such as sensitivity and specificity were evaluated by the receiver-operator characteristics (ROC) curve at optimal cut-off values. The optimal cut-off values were determined at the maximal point of the area under the curve. RESULTS: The sensitivity and specificity of anti-CCP were 72.8% and 92% at 3.8 U/mL. The sensitivity and specificity of RF were 80.6% and 78.5% at 9 U/mL. The sensitivity and specificity of anti-CCP and RF were 67%, 95.2% and 63.3%, 90% at 8.4 U/mL, 20 U/mL, respectively. A combination of anti-CCP with RF increased the sensitivity and specificity to 79.3%, 96.4%, respectively. Anti-CCP was positive in 23.8% among 63 sero-negative RA patients. CONCLUSIONS: We considered that the anti-CCP might be useful as another new serological marker for the diagnosis of a RA combination with RF, or not, because the anti-CCP has a higher diagnostic specificity than the RF and was an easy, convenient ELISA method in performance.

Discrepant results by High Protein Anti-D and Low Protein Anti-D in a D Negative Newborn / 대한임상병리학회지

High-protein anti-D reagents prepared from pools of human serum have been used for routine RhD typing but, low-protein, saline reactive anti-D reagents formulated predominantly with monoclonal antibodies are in current use. Because some of the high-protein reagents contain macromolecular additives that may cause red cells coated with immunoglobulin to aggregate spontaneously, antisera with these additives may produce a false-positive reaction. A four-day old male was admitted due to severe jaundice. Initially, the RhD type of the newborn using a high-protein reagent was D-positive and then, using two low-protein reagents, it was D-negative. The blood type of the mother was B, CDe, and that of the newborn was B, CcdEe. The direct antiglobulin test on the newborn's RBC was positive. Anti-E and anti-c were identified in the mother's serum and anti-E only was identified in the newborn's serum. The newborn was treated with phototherapy for 10 days and discharged as recovered. We present a case of hemolytic disease of the D negative newborn, which showed a discrepancy between high protein anti-D and low protein anti-D. With a review of literature, the newborn was possibly misinterpreted as D positive.