[Assessment of normal growth patterns in rats by Z score]

Malnutrition is one of the most important causes of normal growth disruption. Anthropometric methods are highly valuable in clinic pediatric diagnosis to determine the nutritional status of children and as recovery monitoring. In previous studies, we have demonstrated that the standards weight-age, height-age and weight-height of growing rats had similar distribution to those in normal children. However, to improve the diagnostic effectiveness of anthropometric information, statistical analysis to normally and non-normally distributed variables should be applied. One hundred Wistar rats (50 male and 50 female rats) from weaning (day = 25, weight = 35-40 g) to 70 days of age were fed with a commercial diet. Water and diet were offered "ad libitum". Body weight and height were recorded every two or four days, respectively. Percentiles of weight vs age, height vs age and weight vs height were plotted for male and female rats. The statistical criterion for classifying the anthropometric measurements into nutritional categories was based on percentiles cutoff and Z-score. The Z-score was calculated according to: Z = (standard mean value-subject value/standard deviation of standard). The statistical anthropometric categories of growing rats were similar to those obtained in children. This evidence suggest that the rat can be used as an experimental model to infer and predict the nutritional response in children.