Abstract:

Objective To investigate the combined determination of glucose-6-phosphate isomerase（GPI）,anti-cyclic citrulinated peptide（CCP） antibody and rheumatoid factor（RF） for the diagnosis of rheumatoid arthritis（RA）. Methods A total of 60 RA patients were enrolled,and 60 non-RA patients were enrolled,including 28 patients with systemic lupus erythematosus （SLE）,22 patients with ankylosing spondylitis（AS） and 10 patients with osteoarthritis （OA）. A total of 30 healthy subjects were enrolled as healthy control group. GPI and anti-CCP antibody were determined by enzyme-linked immunosorbent assay,and RF was determined by turbidimetric immunoassay. Erythrocyte sedimentation rate（ESR） and C-reactive protein（CRP）were also determined. Disease activity score in 28 joints（DAS28）was used. Receiver operating characteristic （ROC）curve was used to define optimal threshold of GPI for the diagnosis of RA. Pearson correlation analysis was used to evaluate the correlations of GPI,anti-CCP antibody and RF with ESR,CRP and DAS28. Results There was statistical significance for RA and non-RA groups compared with healthy control group（P<0.05）. There was statistical difference for GPI,anti-CCP antibody and RF in RA group compared with non-RA group（P<0.05）. ROC curve showed that the optimal threshold of GPI was 0.28 mg/L for the diagnosis of RA,the sensitivity was 82.2%,the specificity was 89.5%,and the area under ROC curve was 0.87. The positivity of combined determination was defined as each index （GPI,anti-CCP antibody and RF） was positive,and the sensitivities and specificities of GPI and anti-CCP antibody single determinations were higher than those of RF single determination. The sensitivity of the combined determination was the lowest,but the specificity was the highest （99.9%）. There were 8 anti-CCP antibody-negative patients in RA group,its concentration of GPI was 0.757（0.001-3.001）μg/mL,and its positive rate was 87.5%. GPI was positively correlated with ESR, CRP and DAS28 in RA group （r=0.117,0.041 and 0.104,P<0.001）. Conclusions GPI can be used as an indicator for the diagnosis of RA and distinguishing RA activeness,especially for RA patients with negative anti-CCP antibody. The combined determination of GPI,anti-CCP antibody and RF can improve specificity in the diagnosis of RA.

Key words: Glucose-6-phosphate isomerase, Anti-cyclic citrulinated peptide antibody, Rheumatoid factor, Rheumatoid arthritis