A comparison of the National Center for Health Statistics and new World Health Organization growth references for school-age children and adolescents with the use of data from 11 low-income countries

BACKGROUND: In 2007 new WHO growth references for children aged 5-19 years were introduced to replace the NCHS references. OBJECTIVE: The study aimed to compare the prevalence of stunting, wasting and thinness estimated by the NCHS and WHO growth references. DESIGN: NCHS and WHO height-for-age z-scores were calculated using cross-sectional data from 20,605 schoolchildren aged 5-17 years in 11 low income countries. The differences in the percentage of stunted children were estimated for each year of age and sex. Z-scores of BMI-for-age and weight-for-height were calculated using the WHO and NCHS references respectively to compare differences in the prevalence of thinness and wasting. RESULTS: No systematic differences in mean z-scores of height-for-age were observed between the WHO and NCHS growth references. However, z-scores of height-for-age varied by sex and age, particularly during early adolescence. Among children for whom weight-for-height could be calculated, the estimated prevalence of thinness (WHO reference) was consistently higher than the prevalence of wasting (NCHS reference) by as much as 9% in girls and 18% in boys. CONCLUSION: In undernourished populations, the application of the WHO (2007) references may result in differences in the prevalence of stunting for each sex compared with using the NCHS references, as well as a higher estimated prevalence of thinness compared with wasting. An awareness of these differences is important for comparative studies or when evaluating programs. For school-age children and adolescents across all ranges of anthropometric status, the same growth references should be applied when undertaking such studies.