[Significance of glucose-6-phosphate isomerase assay in early diagnosis of rheumatoid arthritis].
OBJECTIVE
To explore the titer of glucose-6-phosphate isomerase (GPI) for early diagnosis of the outpatient with rheumatoid arthritis (RA) in real life, and to analyze its relationship with disease activity.


METHODS
In the study, 1 051 patients with arthritis were collected in the group who had joints tender and swelling, and 90 cases of healthy people as a control group. ELISA method was used to detect the serum level of GPI, and according to clinical features and laboratory test, all the patients including 525 RA patients, the other patients including osteoarthritis (OA), 134 cases of seronegative spine joint disease (SpA), 104 cases of systemic lupus erythematosus (SLE), 31 cases of primary Sjogren syndrome (pSS), 24 cases of gout arthritis (GA), 22 cases of other connective tissue diseases (including polymyalgia rheumatica, dermatomyositis, systemic sclerosis, adult Still disease) and 46 cases of other diseases (including 165 cases of osteoporosis, avascular necrosis of the femoral head, traumatic osteomyelitis, bone and joint disease, juvenile rheumatoid arthritis, tumor). The diagnostic values of GPI were assessed, and the differences between the GPI positive and negative groups of the RA patients in clinical characteristics, disease activity, severity and inflammatory index analyzed.


RESULTS
The positive rate of serum GPI in the patients with RA was 55.4%, contrasting to other autoimmune diseases (14.3%) and healthy controls (7.78%)(P<0.001). Compared with the OA and SpA patients, the RA group was increased more significantly, and the difference was statistically significant (P<0.001). The diagnostic value of GPI alone for RA was 0.39 mg/L, the sensitivity was 54.2%, and specificity was 87.3%. The positive rate of GPI in RF negative patients was 36.1%; the positive rate of GPI in anti-CCP antibody negative patients was 34.2%; the positive rate of GPI in RF and anti-CCP antibody negative patients was 24.1%. The level of GPI had positive correlation (P<0.05) with ESR, RF, anti-CCP antibody and HRF-IgG.


CONCLUSION
GPI is sensitive in the patients with RA; GPI positive is important in the diagnosis of RA with anti-CCP antibody and/or RF negative patients. The titer of GPI is related with disease activity of RA.