Measuring the nutritional status of children with juvenile idiopathic arthritis using the bioelectrical impedance method.

OBJECTIVE: To assess the nutritional status of children with juvenile idiopathic arthritis (JIA) using anthropometric measurements and bioelectrical impedance.
METHODS: Twenty-two consecutive JIA patients (seven pauciarticular, 15 polyarticular) attending the rheumatology clinic at Booth Hall Children's Hospital were compared with 22 age- and sex-matched controls attending the accident and emergency department of the same hospital. There were no patients with systemic-onset JIA in the cohort. Height, weight, head circumference and skinfold thickness at four sites (biceps, triceps, subscapular and suprailiac) were measured. Regression equations were used to calculate body fat as a percentage of weight, and arm muscle circumference. In addition, bioelectrical impedance measurements were made using a Holtain body composition analyser. These measurements were then used to calculate the total body water, which could be used as an indirect estimate of the lean body mass.
RESULTS: Of the JIA patients, 22.7% were below the third centile for height, 18.1% had a weight less than the third centile. Mid-arm circumference was below the fifth centile in 36.4% of the patients. Patients with polyarticular disease showed significantly more signs of malnutrition than patients with pauciarticular disease. In the polyarticular group, comparison with controls revealed significant P values for reduction in height (0.047), weight (0.045), mid-arm circumference (0.002), arm muscle circumference (0.012), percentage body fat (0.008) and total body water (0.031).
CONCLUSIONS: In view of the findings of lower total body water, indicating lower lean mass, in more nutritionally deprived JIA patients (as deduced by the other physical parameters measured), we conclude that bioelectrical impedance is a useful adjunct to anthropometric measures in assessing nutritional status in JIA.