Study of the serum level of receptor activator of nuclear factor–kappa B ligand (RANKL)‎ and osteoprotegerin (OPG)‎ in patients with rheumatoid arthritis

الملخص EN

Introduction : Rheumatoid arthritis (RA) is a highly osteodestructive disease.

Three forms of bone disease have been described in RA : focal bone loss, per articular osteopenia and generalized osteoporosis.

Aim : This work aimed to estimate the serum levels of receptor activator of nuclear factor kappa B ligand (RANKL) and osteoprotegerin (OPG) in RA patients and to correlate their levels with the clinical activity and radiological findings.

The present study was conducted on 67 subjects, divided in two groups: patients group involving 45 RA patients (41 females and 4 males) and their mean age was 44.7 ± 9.4 years and control group involving 22 normal volunteer subjects (20 females and 2 males) and their mean age was 45.5±8.1 years.

Methods : To all subjects the following parameters were carried out : A thorough history taking and full physical examination with special stress on joint and extra-articular manifestations of RA, calculation of the disease activity score (DAS28) , plain X-rays for both hands and wrists, laboratory investigations including: complete blood count (CBC), estimation of serum levels of total calcium, ionized calcium, inorganic phosphate, C-reactive protein (CRP), as well as detection of soluble RANKL and OPG, antideoxyribonucleo protein antibodies (anti-DNA) and Rose-Waaler test for detection of rheumatoid factor (RW).

Results : The mean serum ionized calcium (Ca++) and the haemoglobin levels and red blood cell count were significantly lower in patients group than in controls.

Platelet count showed significant increase in patients group.

Erythrocyte sedimentation rate (ESR), RW, CRP, RANKL, OPG and RANKL / OPG ratio were significantly higher in patients group than that in controls.

There was a significant positive correlation between OPG levels, the duration of the disease and the presence of positive x-ray findings.

A significant positive correlation was found between RANKL / OPG ratio and both RW and the disease activity.

All patients with high disease activity had morning stiffness more than 30 minutes and 79.4% of them had positive x-ray findings.

Conclusion : From the previous results it could be concluded that RANKL is a key mediator of joint destruction and bone loss in RA and can be used as a diagnostic marker for bone erosion and disease activity.

OPG plays a protective role against bone erosion and joint destruction, which are mediated by high RANKL level.