Elevated serum 14-3-3η protein may be helpful for diagnosis of early rheumatoid arthritis associated with secondary osteoporosis in Chinese population.

Osteoporosis (OP) is one of the signs of bone damage in rheumatoid arthritis (RA). The 14-3-3η protein is an inflammatory protein, which has been reported to be associated with rheumatoid arthritis (RA). This is to determine the serum levels of 14-3-3η protein, evaluate its diagnostic value in early RA, and clear out its significance in RA with secondary osteoporosis. Two hundred fifty-nine RA patients and 80 age and sex-matched healthy controls were included. Assays of serum 14-3-3η protein were done for all participants by enzyme-linked immunosorbent assay (ELISA). Dual-energy X-ray absorptiometry (DEXA) was used to measure bone mineral density (BMD). Serum 14-3-3η protein level was significantly high in RA (2.49/4.72), compared with controls (P < 0.0001). Positive rate of 14-3-3η protein in RA was 97.3%, which was higher than that in controls (χ  = 276.641, P < 0.0001). Serum 14-3-3η protein level in early RA was significantly higher than that in established RA (3.91/4.82 vs 2.01/3.29, Z = 2.624, P < 0.05). The positive rate among three groups (normal control, early RA group, established RA group) differed from each other (χ  = 131.396, P < 0.0001). Results of ROC curve indicated the cutoff point of 14-3-3η protein for diagnosis of early RA was 0.879 ng/ml (P < 0.0001). Linear correlation analysis found that serum 14-3-3η protein positively correlated with VAS and HAQ (P < 0.0001), negatively correlated with BMD at lumbar spine and femur in RA (P < 0.0001). Serum 14-3-3η protein among groups of bone mass normal (2.73/3.79), osteopenia (3.15/4.86), and osteoporosis (6.34/6.42) was different in early RA patients (χ  = 7.974, P < 0.05). Serum 14-3-3η protein levels increase significantly in patients with RA (especially in early RA). There are close relationships between serum 14-3-3η protein and clinical symptoms and osteoporosis in patients with RA.