Study of bone formation marker levels in rheumatoid arthritis

Abstract

Background: Rheumatoid arthritis (RA) is an autoimmune disease of unknown cause that affects the joints principally. The disease affects between 0.5% and 1% of the adult population worldwide. Two to three times as many women as men suffer from the disease. Osteocalcin (OC) is a small protein of 49 amino acids long. OC is the most abundant non-collagenous protein in bone. OC originates from osteoblasts and is deposited into bones or released into circulation, where it correlates with histological measures of bone formation. Bone alkaline phosphatase (ALP) is a glycoprotein that is found on the surface of osteoblasts. This enzyme reflects the biosynthetic activity of these bone-forming cells. The presence of OC and ALP in the circulation may, therefore, provide a specific chemical index of osteoblastic activity. Objectives: This study was undertaken to estimate the values of serum OC and ALP among patients with RA and healthy control groups and to compare and find out any changes in levels of serum OC and ALP between the study and control groups. Materials and Methods: It was a case–control study done on 76 RA patients and 76 age- and sex-matched healthy individuals. Serum OC and serum ALP values were evaluated among all 76 cases and 76 controls. Serum OC was measured using immunoenzymatric assay and ALP was measured by colorimetric method. Statistical analysis was performed and results were tabulated and analyzed. Results: Mean ± standard deviation of serum OC level is significantly higher (P < 0.001) among cases (18.50 ± 8.72 ng/ml) than controls (9.98 ± 7.68 ng/ml). Similarly, the values of ALP are higher (P < 0.001) among cases (216.22 ± 59.96 IU/L) than controls (164.17 ± 50.70 IU/L). A significantly positive correlation was found between serum OC and serum ALP levels. Patient with the highest mean value of serum OC also has the highest values of ALP. The values of serum ALP and OC levels increase significantly in both early and late stages when compared with control values. Conclusions: A significant difference between the values of serum OC and ALP among cases and controls was seen in the study. Levels of both these parameters are elevated in subjects with RA compared to controls. Furthermore, the levels of serum OC correlated with the levels of serum ALP. This study demonstrates that increased bone formation is associated with RA together with bone resorption.