Upper arm measurements of healthy neonates comparing ultrasonography and anthropometric methods

Objective: To compare measurements of the upper arm cross-sectional areas ( total arm area, arm muscle area, and arm fat area of healthy neonates) as c alculated using anthropometry with the values obtained by ultrasonography. Materials and methods: This study was performed on 60 consecutively born he althy neonates: gestational age (mean+/-SD) 39.6+/-1.2 weeks, birth weight 3287.1+/-307.7 g, 27 males (45%) and 33 females (55%). Mid-arm circumferenc e and tricipital skinfold thickness measurements were taken on the left upp er mid-arm according to the conventional anthropometric method to calculate total arm area, arm muscle area and arm fat area. The ultrasound evaluatio n was performed at the same arm location using a Toshiba sonolayer SSA-250A (R), which allows the calculation of the total arm area, arm muscle area an d arm fat area by the number of pixels enclosed in the plotted areas. Stati stical analysis: whenever appropriate, parametric and non-parametric tests were used in order to compare measurements of paired samples and of groups of samples. Results: No significant differences between males and females w ere found in any evaluated measurements, estimated either by anthropometry or by ultrasound. Also the median of total arm area did not differ signific antly with either method (P = 0.337). Although there is evidence of concord ance of the total arm area measurements (r = 0.68, 95% CI: 0.55-0.77) the t wo methods of measurement differed for arm muscle area and arm fat area. Th e estimated median of measurements by ultrasound for arm muscle area were s ignificantly lower than those estimated by the anthropometric method, which differed by as much as 111% (P < 0.001). The estimated median ultrasound m easurement of the arm fat was higher than the anthropometric arm fat area b y as much as 31% (P < 0.001). Conclusion: Compared with ultrasound measurem ents using skinfold measurements and mid-arm circumference without further correction may lead to overestimation of the cross-sectional area of muscle and underestimation of the cross-sectional fat area. The correlation betwe en the two methods could be interpreted as an indication for further search of correction factors in the equations. (C) 1999 Elsevier Science Ireland Ltd All rights reserved.