Construction of Lambda, Mu, Sigma Values for Determining Mid-Upper Arm Circumference z Scores in U.S. Children Aged 2

Susan M Abdel-Rahman1, Charlie Bi2, Kristi Thaete3

  • 11 University of Missouri, Kansas City-School of Medicine and Section of Therapeutic Innovation, Division of Clinical Pharmacology, Toxicology, and Therapeutic Innovation, Children's Mercy Hospital, Kansas City, Missouri, USA.

Insights

New Lambda Mu Sigma (LMS) values enable mid-upper arm circumference (MUAC) z-score calculations for U.S. children up to 18 years. This advances malnutrition assessment, improving pediatric nutrition monitoring.

Area of Science:

  • Pediatric Nutrition
  • Anthropometry
  • Growth Monitoring

Background:

  • Mid-upper arm circumference (MUAC) is a key indicator for malnutrition, outperforming BMI z scores in predicting morbidity and mortality.
  • A consensus recommends MUAC z scores for U.S. children, but data for those over 5 years were lacking.

Purpose of the Study:

  • To generate Lambda Mu Sigma (LMS) values for calculating MUAC z scores in U.S. children aged 2 months to 18 years.
  • To provide essential data for comprehensive pediatric nutrition assessment.

Main Methods:

  • Utilized National Health and Nutrition Examination Survey (1999-2012) anthropometric data (n=28,995) for model development.
  • Constructed smoothed centiles and validated using independent U.S. MUAC datasets (n=1438).
  • Assessed goodness-of-fit using visual and statistical methods, including detrended quantile-quantile plots and Q statistics.

Main Results:

  • Generated LMS curves demonstrated excellent fit to the raw data across all age groups, including infants under 12 months.
  • The derived curves aligned with existing CDC percentiles.
  • The distribution of z scores closely approximated the expected 0 ± 1 across all age groups.

Conclusions:

  • The developed LMS values provide a reliable method for clinicians to calculate MUAC z scores for U.S. children.
  • This facilitates improved nutritional status monitoring and early identification of malnutrition in pediatric populations.
Abstract

Related Concept Videos

z Scores and Area Under the Curve01:17

z Scores and Area Under the Curve

z scores are the standardized values obtained after converting a normal distribution into a standard normal distribution. A z score is measured in units of the standard deviation. The z score tells you how many standard deviations the value x is above (to the right of) or below (to the left of) the mean, μ. Values of x that are larger than the mean have positive z scores, and values of x that are smaller than the mean have negative z scores. If x equals the mean, then x has a z score of...
19.9K
z Scores and Unusual Values01:07

z Scores and Unusual Values

The z score is one of the three measures of relative standing. It describes the location of a value in a dataset relative to the mean. z scores are obtained after the standardization of the values in a dataset. The z score for the mean is 0.
 This score indicates how far a value is from the mean in terms of standard deviation. For example, if a data value has a z score of +1, the researcher can infer that the particular data value is one standard deviation above the mean. If another data...
11.5K
Introduction to z Scores01:05

Introduction to z Scores

A z score (or standardized value) is measured in units of the standard deviation. It indicates how many standard deviations the value x is above (to the right of) or below (to the left of) the mean, μ. Values of x that are larger than the mean have positive z scores, and values of x that are smaller than the mean have negative z scores. If x equals the mean, then x has a zero z score. It is important to note that the mean of the z scores is zero, and the standard deviation is one.
z scores...
1.5K
Introduction to z Scores01:06

Introduction to z Scores

A z score (or standardized value) is measured in units of the standard deviation. It tells you how many standard deviations the value x is above (to the right of) or below (to the left of) the mean, μ. Values of x that are larger than the mean have positive z scores, and values of x that are smaller than the mean have negative z scores. If x equals the mean, then x has a zero z score. It is important to note that the mean of the z scores is zero, and the standard deviation is one.
z scores...
11.7K
Critical Values01:31

Critical Values

A critical value is a definite value obtained from a particular probability distribution at a predecided confidence level (or a predecided significance level) for a given population parameter. The critical value provides demarcation that separates the sample statistics that are likely to occur from the ones that are unlikely to occur based on the given probability distribution and the population parameter to be estimated. The critical value for normal distribution is obtained from the z...
10.6K
Wald-Wolfowitz Runs Test II01:17

Wald-Wolfowitz Runs Test II

The Wald-Wolfowitz runs test, commonly referred to as the runs test, is a nonparametric test used to assess the randomness of ordered data. The test evaluates the number of runs, which are consecutive sequences of similar elements within the data. If the number of runs is significantly higher or lower than expected, the data is considered non-random, indicating a detectable pattern or structure.
For binary data, runs are identified using symbols such as + and −, or equivalently, 1s and 0s. In...
608