Validity of Weech's formulae in detecting undernutrition in children

Primary care physicians in developing countries frequently use Weech's formulae to estimate the expected weight and height of children using age as a variable. The present study was undertaken to assess the validity of Weech's formulae in diagnosing undernutrition. We collected anthropometric information from 294 consecutive children, aged 12-59 months, who visited a health centre. Age was calculated from birth records and was recorded in completed months as well as completed years. Weight and height/length were measured using standard methods. Weight-for-age and height-for-age Z scores were calculated using WHO Anthro. Weech's formulae were used to calculate weight-for-age (%) and height-for-age (%). A cut off of < or =80.0% weight-forage and < or = 95.0% height-for-age were used to evaluate the validity of underweight and stunting respectively; a cut off of < or = 60.0% weight-for-age and <85.0% height-for-age were used for severe underweight and severe stunting respectively. Weech's formulae were found to be 100% sensitive in detecting underweight (weight-for-age Z score<-2) and stunting (height-for-age Z score<-2). When evaluating severe underweight (weight-for-age Z scorc<-3) and severe stunting (height-for-age Z scorc<-3), Weech's formulae were found to be 100% specific but the sensitivity was very low, 25.0% and 15.4% respectively. Based on the findings of our study Weech's formulae appear to be a sensitive tool to detect underweight and stunting in children between 12-59 months of age. Such formulae should however be used with caution when evaluating severe forms of undernutrition.