Thus the only choice available for a clinician and it is a highly serviceable one is converting the childs weight for age to a z score and tracking it over time. Absence of acute protein energy malnutrition or normal nutritional status is defined as having a weight for height z score of 20 or greater. At these extremes the z score is a more precise reflection of how far the measurement deviates from the mean and is a useful tool for tracking changes. The expected ranges of standard deviations of the z score distributions for the three anthropometric indicators are as follows 5. Predicted percentiles and z scores much over the 95th percentile using the cdc charts may be inaccurate. Moderate acute protein energy malnutrition is defined as having a weight for height z score of 30 to less than 20.
One data point mid upper arm 1 to 19 2 to 29 3 circumference heightlength for age 3 z score bmi for age z score 1 to 19 2 to 29 3 weight for 1 to 19 2 to 29 3 heightlength z score malnutrition mild moderate severe. Weight for length or weight for height that is calculated based on inaccurate lengths or heights is also inaccurate. Eg 8 4 for 8 lb and 4 oz height. To enter years and months enter y m. It is not valid for standing height. More simply z score score mean sd.
However in case of nutrition we usually calculate z score for weight for height height for age and weight for age. The same difference is found between a z score of 0 and a z score of 1 on the same distribution. At the extremes 98th percentile or 2nd percentile small differences in percentiles represent clinically important differences in weightheight. Interpreting the results in terms of z scores has several advantages. Valid ages from 2 to 20 years age. Eg 4y 5m weight.
Z score can be used in different fields wherever statistical measurement is required. Head circumference for age and older children weight for stature. Slower weight gain from age 3 12 months deviation of growth occurs when babies are already on solids ie not deficiency less effect on length than weight at 2 years average weight close to reference. For example on the height for age distribution for a 36 month old boy the distance from a z score of 2 to a z score of 1 is 38 cm. The values corresponding to specific z scores 2 15 1 050 051152 are contained in 8 excel data files representing the 8 different growth curves for infants weight for age. To enter pounds and ounces enter.
The z score scale is linear and therefore a fixed interval of z scores has a fixed height difference in cm or weight difference in kg for all children of the same age. Available means and sds of z scores of survey data are being included in the global database. Dewey kg et al. Nutr clin pract november 2014 doi.
Gallery of Weight For Height Z Score Interpretation
