Growth reference choice affects estimates of growth deficit prevalence in a developing country

The National Center for Health Statistics/World Health Organization (NCHS/WHO) international growth reference has been the main reference used worldwide for over 20 years. In 2000, the Centers for Disease Control and Prevention (CDC) published a new growth reference for children aged 0-20 years in the US; in 2006, the new WHO Child Growth Standards were published for children 0-5 years. Currently, the WHO continues to promote use of the 1977 NCHS/WHO reference for school-age children. The main objective of this study was to evaluate differences in the prevalence of growth deficits estimated using the 2000 CDC reference vs. the 1977 NCHS/WHO reference. We used data from 419 school children, 6-9 years of age, collected as part of a cross-sectional study performed by the Instituto de Nutrición de Centro América y Panamá (INCAP) in 2000, in rural communities of the Pacific coast of Guatemala. Z-scores and percentiles from each growth reference were used to estimate the prevalence of growth deficits; for each growth index, the prevalence of deficits corresponding to the NCHS/WHO and CDC references was compared. The two references generated substantially different estimates of growth deficit frequencies. For every growth index, the newer CDC reference classified Guatemalan children as a group at lower z-scores and percentiles than the NCHS/WHO reference; prevalence differences were 1.4, 6.9, and 11.5 percent for wasted/thin, stunted, and underweight, respectively (defined as z-score <-2). Estimates based on the CDC reference were on average 0.16 to 0.31 z-score units lower than the NCHS/WHO reference (depending on the index compared), thus characterizing the same children with poorer growth. The two references are not interchangeable; the discrepancies raise questions about the appropriateness of comparing growth deficit prevalence in industrialized and developing countries when different references are used. The choice of growth reference will substantially impact the assessment of growth in children and resulting policy aimed at improving childhood growth. A universally appropriate standard is clearly needed for school-aged children.