Classification of nutritional status as 'Z score' or per cent of reference median--does it alter mortality prediction in malnourished children?
The objective of the study was to evaluate, using a prospective cohort study, whether classification of nutritional status by 'Z score' or per cent of reference median alters the prediction of death in malnourished children. The subjects were children with diarrhoea requiring hospitalization due to moderate or severe dehydration and/or associated complications. There were 382 participants under 5 years of age, of whom 37 died (cases), 320 were discharged in a satisfactory condition (controls) and 25 left before diarrhoea was completely cured (lost to follow-up--excluded). Rehydrated weight and recumbent length (under 2 years) or standing height were recorded and the three indices (weight for age, height for age and weight for height) derived as both 'Z scores' and per cents of reference National Centre for Health Statistics (NCHS) medians. Logistic regression, sensitivity specificity curves and Zda test for normalized distances were used to compare the relative utility of these two classification methods in identifying children with a high risk of dying. The per cent of reference median and 'Z scores' were highly correlated (r = 0.9540, 0.9787 and 0.9667, respectively). Both methods yielded virtually identical results in predicting death of malnourished children for all the three indices. It was concluded that 'Z score' and per cent classification of nutrition are equally efficient in predicting death of malnourished children.