HWWAZWHO (HW71) is a 4-digit numeric variable with 2 implied decimal places.
9995 = Height out of plausible limits
9996 = Age in days out of plausible limits
9997 = Flagged cases
9998 = Missing
9999 = NIU (not in universe)
For surviving children born in the three to five years before the survey, HWWAZWHO (HW71) reports the difference between the child's weight and the median weight of a reference population of the same age and sex, expressed in units equal to one standard deviation of the reference population's distribution. An anthropometry measure expressed in reference standard deviation units is also known as a Z-score. HWWAZWHO values are reported in units equal to 100 times the Z-score, to preserve two decimal places without requiring the use of a decimal point. Dividing HWWAZWHO by 100 will yield a child's weight-for-age Z-score (WAZ) value.
Low child weight-for-age, or "underweight," is a composite indicator of acute and/or chronic malnutrition. The WHO Global Database on Child Growth and Malnutrition considers a weight-for-age Z-score (WAZ) between -2 and -3 to represent moderate malnutrition, and WAZ below -3 to represent severe malnutrition.
Reference populations used to generate HWWAZWHO draw from the WHO Multicenter Growth Reference Study (MGRS) released in 2006, which defined new standard anthropometry curves using a globally diverse reference population intended to reflect healthy growth conditions. For DHS samples that preceded WHO MGRS release, DHS retroactively calculated weight-for-age Z scores using WHO MGRS reference data.
Prior to the WHO MGRS, DHS anthropometry reference populations drew from 1978 U.S. CDC National Center for Health Statistics (NCHS) international growth reference data, which was the previous international standard reference. The DHS variable HWWAZNCHS (HW8) reports the child's weight-for-age Z-score value using the NCHS/CDC 1978 reference population. DHS has continued to release versions of all child anthropometric variables using NCHS/CDC 1978 reference populations, to preserve comparability with samples preceding the 2006 WHO MGRS release.
Apart from universe differences, HWWAZWHO (HW71) has no comparability problems.
Comparability - Standard DHS
HWWAZWHO (HW71) is included in the standard DHS assessment beginning in Phase 5. For samples that preceded the 2006 WHO MGRS release, DHS retroactively calculated WAZ scores using the WHO MGRS reference population.