Comparison of indicators for assessing wasting among children younger than 5 years: a longitudinal study in northern Kenya

Mid-upper arm circumference (MUAC) or weight-for-height/length Z-score (WHZ) are recommended in wasting diagnosis, but there are discrepancies between these indicators in identifying children as wasted. We compared the extent to which WHZ, MUAC, MUAC-for-age Z-score (MAZ) identify the same children as wasted and assessed the predictors of discordance and concordance in wasting diagnosis by these indicators using data from a longitudinal study of children younger than 3 years at recruitment in Turkana and Samburu counties. Wasting prevalence was consistently lower based on MUAC than WHZ and MAZ. Compared to WHZ, MAZ had higher sensitivity than MUAC, with the sensitivity of MAZ increasing and MUAC decreasing with age. Both indicators had high specificity. WHZ had a better agreement with MAZ than MUAC in wasting diagnosis. Older children were less likely to be classified as wasted by MUAC alone or by both MUAC and WHZ but were more likely to be classified as wasted by WHZ alone, MAZ alone or by both MAZ and WHZ. Compared to girls, boys were less likely to be classified as wasted by MUAC alone but more likely to be classified as wasted by WHZ alone. Stunted children were more likely to be classified as wasted by MUAC alone, MAZ alone, both MUAC and WHZ, and both MAZ and WHZ but not by WHZ alone. Classifications of wasting based on WHZ, MAZ, and MUAC are age, sex, and stunting status dependent. Compared to WHZ, MAZ is a more reliable and valid indicator than MUAC in these settings.