Advances in growth chart design and use: the UK experience.

As part of the process of adopting the WHO standard in the United Kingdom, the Royal College of Paediatrics and Child Health (RCPCH) was commissioned by the UK Department of Health to design new UK-WHO growth charts. The working group for this project combined expertise ranging from statistics and graphic design to qualitative research, as well as paediatrics, nursing and dietetics. New charts for children under 4 years were published in 2009 and are now widely used in the UK and beyond (www.growthcharts.rcpch.ac.uk). This paper will describe what we have learned in general about the process of designing charts and how these principles were applied to the design of a novel chart designed specifically for sick and premature infants. A successful design first requires clarity about the exact purpose of the chart and who will use it. The layout of the chart can then be varied in many ways to fit that use and ensure users are not misled. Users need consistent and well-evidenced rules for chart use. Drafting the instructions serves as a powerful test of the validity and clarity of the design. However, charts need also to be formally evaluated, as expert views will not reflect those of the average user. The Neonatal and Infant Close Monitoring (NICM) chart included various novel design features, including date boxes for gestational age adjustment and low SD lines to help assess very small infants. It was evaluated at three stages using plotting exercises and each phase led to substantial design changes. Growth charts are conceptually very complex, with the capacity to mislead as well as inform and should always be formally evaluated before implementation.