Dual energy X ray absorptiometry and biochemical markers in evaluating bone mineral content in children with juvenile rheumatoid arthritis

ABSTRACT

In this prospective study we aimed to measure the total body bone mineralization by DEXA in the prepubertal patients with JRA. Also measuring some biochemical markers of bone turnover, in a trial to understand the mechanisms of osteopenia in JRA and to find relationships between bone mineral loss, and disease sub type, duration, disease activity and drugs used in treatment Thirty prepubertal patients were included in the study; dual energy X ray absorptiometry were done for all patients, also serum calcium; phosphorous, alkaline phosphatase, serum osteocalcin., serum calcitonin and urinary ca/c ratio, with 18 controls for the biochemical parameters of bone mineralization. Twenty nine patients had BMD fell below the normal regression mean of age and sex. There is positive correlation between age and BMD [r=0.499, p<0.01]. The duration of the disease is significantly higher in patients with severe osteoporosis compared to the patients with severe osteopenia [67.5 122.13 months vs 36 _ 12.75 months with p<0.02]. BMD was significantly affected in patients with active arthritis compared to patients in remission [p= 0.04]. MTX significantly affected the BMD in our work, but no significant effect of low dose of steroids. No difference of BMD between the 3 subtypes of JRA. Serum calcium levels were low but not significant statistically, but there was a positive correlation between BMD and serumCa [p<0.01]. Serum phosphorous and alkaline phosphatase were not affected sign significantly. There was no significant difference in serum osteocalcin between patients and controls. Serum calcitonin levels were significantly lower in patients than controls. Urine ca/cr ratio as a measurement of bone resorption were significantly higher in patients than controls [p=0.03]. Our results, suggest that DEXA is a new promising technique to monitor disease progression. New biochemical markers show contradictory results in different studies. A prospective examination of risk factors for osteoporosis need to he performed and more work to get the best treatment of osteoporosis of JRA