Similarities in Methodology
While there were many differences in the design and methodology between the WHO and CDC chart development, similarities exist.
- Growth curves for both charts were developed using an LMS methodology1-2 to describe both percentiles and z-scores (standard deviation units) although there were some differences in the smoothing techniques used to create the growth curves.
- Data quality was tightly controlled in both studies with precise procedures for training and standardization of measurements using high quality anthropometry equipment. Optimal data entry and cleaning techniques were used.3-4
1Cole TJ. The LMS method for constructing normalized growth standards. Eur J Clin Nutr 1990;44(1):45-60.
2Cole TJ, Green PJ. Smoothing reference centile curves: the LMS method and penalized likelihood. Stat Med 1992;11(10):1305-19.
3de Onis M, Onyanga AW, Van den Broeck J, Chumlea WC, Martorell R for the WHO Multicentre Growth Reference Study Group. Measurement and standardization protocols for anthropometry used in the construction of a new international growth reference. Food Nutr Bull 2004:25 Suppl1:S27-36.
4Kuczmarski RJ, Ogden CL, Guo SS, Grummer-Strawn LM, Flegal KM, Mei Z, Wei R, Curtin LR, Roche AF, Johnson CL. 2000 CDC Growth Charts for the United States: methods and development. Vital Health Stat 11. 2002;(246):1-190.