What can the randomness of missing values tell you about clinical practice in large data sets of children's vital signs?

Currently, there are 5.5 million Emergency Department (ED) attendances in England by Children and Young People making up 26% of all age attendances.1 The Nuffield trust has reported a 9% increase in emergency or unplanned admissions between June 2005 and June 20152 and the Royal College of Paediatrics and Child Health says “attendances of children are projected to increase by 50% by 2030 if current trends are maintained”.1