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Classification of nutritional status as 'Z score' or per cent of reference median--does it alter mortality prediction
H P Sachdev1, L Satyanarayana, S Kumar
1Department of Pediatrics, Maulana Azad Medical College, New Delhi, India.
Insights
Nutritional status classification using Z-scores or percentiles of reference medians are equally effective in predicting mortality risk in malnourished children. This finding aids in accurate risk assessment for pediatric malnutrition interventions.
Area of Science:
- Pediatric Nutrition
- Public Health
- Epidemiology
Background:
- Malnutrition is a significant risk factor for mortality in children, especially those with severe diarrhea and dehydration.
- Accurate nutritional status classification is crucial for identifying high-risk children and implementing timely interventions.
- Existing methods for classifying nutritional status include Z-scores and percentiles of reference medians.
Purpose of the Study:
- To compare the predictive accuracy of Z-scores versus percentiles of reference medians for mortality in hospitalized malnourished children.
- To evaluate whether the method of nutritional status classification impacts the prediction of death in this vulnerable population.
Main Methods:
- A prospective cohort study was conducted with 382 children under 5 years old hospitalized for diarrhea.
- Nutritional indices (weight-for-age, height-for-age, weight-for-height) were derived using both Z-scores and percentiles of National Center for Health Statistics (NCHS) medians.
- Statistical analyses included logistic regression, sensitivity-specificity curves, and Zda tests to compare classification methods.
Main Results:
- Z-scores and percentiles of reference medians showed high correlations across all nutritional indices (r > 0.95).
- Both classification methods produced virtually identical results in predicting mortality risk.
- The predictive performance for identifying children at high risk of death was comparable between Z-scores and percentiles.
Conclusions:
- Z-score and percentile classifications of nutritional status are equally efficient in predicting mortality in malnourished children.
- The choice between Z-scores and percentiles does not significantly alter the identification of high-risk individuals.
- These findings support the interchangeable use of both methods in clinical and public health settings for assessing malnutrition-related mortality risk.
Abstract:
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.