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. Eg 8 4 for 8 lb and 4 oz height. Valid ages from 2 to 20 years age. 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. More simply z score score mean sd. Interpreting the results in terms of z scores has several advantages.
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. Absence of acute protein energy malnutrition or normal nutritional status is defined as having a weight for height z score of 20 or greater. 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. Dewey kg et al. Predicted percentiles and z scores much over the 95th percentile using the cdc charts may be inaccurate. The same difference is found between a z score of 0 and a z score of 1 on the same distribution.
However in case of nutrition we usually calculate z score for weight for height height for age and weight for age. To enter years and months enter y m. Eg 4y 5m weight. It is not valid for standing height. 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. Head circumference for age and older children weight for stature.
Moderate acute protein energy malnutrition is defined as having a weight for height z score of 30 to less than 20. The expected ranges of standard deviations of the z score distributions for the three anthropometric indicators are as follows 5. Nutr clin pract november 2014 doi. To enter pounds and ounces enter. Available means and sds of z scores of survey data are being included in the global database. Z score can be used in different fields wherever statistical measurement is required.
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. 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. At the extremes 98th percentile or 2nd percentile small differences in percentiles represent clinically important differences in weightheight. Weight for length or weight for height that is calculated based on inaccurate lengths or heights is also inaccurate.
Gallery of Weight For Height Z Score Interpretation
