Calculator: Waist Z-scores with NHANES III LMS tables

This page is running a macro package for R hosted on a Shiny server. For both waist circumference (WC) and waist:height ratio (WHtR), it calculates Z-scores and percentiles for children aged 5-19 years based on LMS tables from NHANES III. For details, see: Pediatr Res 2015

The sample.csv file shows the expected variable names and formats. Column order is immaterial, but names are case sensitive. The computational algorithm follows that recommended by WHO for skew distributions, with Z scores outside of the range [-3, 3] calculated in units of SD23, the distance between Z=2 and Z=3 (Z = -2 to -3 in the lower tail). Z-scores < -6 or > 6 are not reported (biologically implausible values).

Please note that waist circumference is measured at the level of the iliac crest in the mid-axillary line following the so-called 'NIH' protocol. In a Canadian context, Jennifer Patry-Parisien and colleagues (2012) at Statistics Canada published a formal comparison of alternate measurement protocols and noted that "the Canadian clinical practice guidelines on the management and prevention of obesity in adults and children suggested that practitioners use the National Institutes of Health (NIH) method to measure WC. Two years later, the Canadian Society for Exercise Physiology (CSEP) adopted the NIH method as part of the measurement protocols in the Canadian Physical Activity and Fitness Lifestyle Approach".

The variable agemons is age in months and will be rounded to the nearest integer value; sex may be coded as M/F or m/f or 1/2 (1 = male); height is in cm, and waist is the circumference in cm measured at the level of the iliac crest in the mid-axillary line. The identifier variable id should be unique for each observation.

A spreadsheet with comma separated variables (.csv) may be created using the 'Save As' .csv option in Excel and uploaded using the sidebar on the left. Once results are displayed, download them by clicking the <Download> button, which will typically save them to your Download folder with 'out_' prepended to the original dataset name.

Download Results

As explained in our general FAQ, European computers sometimes use a semicolon to separate columns even though you asked for comma separated variables, which is easy to diagnose by opening your .csv file in a text editor, such as NotePad or TextEdit. If you encounter this problem, there is now a selector in the sidebar for comma, semicolon, or tab delimiters. Please refresh your browser page before changing this selection.