Research Article: Prognostic Accuracy of WHO Growth Standards to Predict Mortality in a Large-Scale Nutritional Program in Niger

Date Published: March 3, 2009

Publisher: Public Library of Science

Author(s): Nathanael Lapidus, Francisco J Luquero, Valérie Gaboulaud, Susan Shepherd, Rebecca F Grais, Andrew Seal

Abstract: BackgroundImportant differences exist in the diagnosis of malnutrition when comparing the 2006 World Health Organization (WHO) Child Growth Standards and the 1977 National Center for Health Statistics (NCHS) reference. However, their relationship with mortality has not been studied. Here, we assessed the accuracy of the WHO standards and the NCHS reference in predicting death in a population of malnourished children in a large nutritional program in Niger.Methods and FindingsWe analyzed data from 64,484 children aged 6–59 mo admitted with malnutrition (<80% weight-for-height percentage of the median [WH]% [NCHS] and/or mid-upper arm circumference [MUAC] <110 mm and/or presence of edema) in 2006 into the Médecins Sans Frontières (MSF) nutritional program in Maradi, Niger. Sensitivity and specificity of weight-for-height in terms of Z score (WHZ) and WH% for both WHO standards and NCHS reference were calculated using mortality as the gold standard. Sensitivity and specificity of MUAC were also calculated. The receiver operating characteristic (ROC) curve was traced for these cutoffs and its area under curve (AUC) estimated. In predicting mortality, WHZ (NCHS) and WH% (NCHS) showed AUC values of 0.63 (95% confidence interval [CI] 0.60–0.66) and 0.71 (CI 0.68–0.74), respectively. WHZ (WHO) and WH% (WHO) appeared to provide higher accuracy with AUC values of 0.76 (CI 0.75–0.80) and 0.77 (CI 0.75–0.80), respectively. The relationship between MUAC and mortality risk appeared to be relatively weak, with AUC = 0.63 (CI 0.60–0.67). Analyses stratified by sex and age yielded similar results.ConclusionsThese results suggest that in this population of children being treated for malnutrition, WH indicators calculated using WHO standards were more accurate for predicting mortality risk than those calculated using the NCHS reference. The findings are valid for a population of already malnourished children and are not necessarily generalizable to a population of children being screened for malnutrition. Future work is needed to assess which criteria are best for admission purposes to identify children most likely to benefit from therapeutic or supplementary feeding programs.

Partial Text: In 2006, the World Health Organization (WHO) introduced the Child Growth Standards for assessing the growth and development of children from birth to 60 mo of age, in order to improve upon the 1977 National Center for Health Statistics (NCHS) international reference. Important differences have been highlighted in the diagnosis of malnutrition when comparing the WHO standards to the NCHS reference [1], their impact on measured prevalence of acute malnutrition (the use of WHO standards generally involves a significant increase in the prevalence of severe malnutrition) [2], and their operational implications (resources and program costs are consequently increased) [3]. However, the relationship of the two growth references with respect to their sensitivity and specificity as a prognostic indicator for mortality has not yet been studied. Findings in this area are important, as malnutrition remains a global public health problem and decisions about recommended indicators may have a major impact on costs and number of children included in programs worldwide.

Data from 64,484 children were analyzed. There were more girls (55.5%) admitted to the program than boys. The average age at admission was 19.5 mo (standard deviation 8.6). The total number of deaths during care was 438. The highest proportion of deaths occurred in the youngest age group (6–11 mo) (16.8%; 95% confidence interval [CI] 14.3–19.8%) (Table 1). Most children were moderately malnourished (94.8% had a weight higher than 70% of the NCHS median) and the mean MUAC was 124 mm (3.0% with MUAC <110 mm). Table 2 displays anthropometric indicators calculated from measurements on children at admission. Only 13 children had a HIV-positive serology, and none of them died during the study period. In a population of malnourished children admitted to an MSF nutritional program, the results suggest that WH using WHO standards was the best indicator to predict mortality under treatment with Z score and percentage of median providing nearly the same performance. Regarding the NCHS reference, the results are consistent with previous studies finding that WH% (NCHS) performed better than WHZ (NCHS) to predict mortality [9]. Source: http://doi.org/10.1371/journal.pmed.1000039

 

Leave a Reply

Your email address will not be published.