Whilst recognising the loss of information with such a procedure, there may be particular applications where a single derived variable can convey the essence of features inherent in the longitudinal form of the data. Rowell and Walters 2 have provided an early systematic review of derived variable analysis. Average steady state measurements' have entered the common vocabulary of sickle cell research without a pertinent examination of the statistical rationale behind such a summary measure. Fundamentally, the choice of derived variable should reflect the research question. It is possible that alternative derived variables may be of benefit to sickle cell research over and above that conferred by the mean summary in certain situations.
Objectives Identify the widespread use of derived variables in sickle cell research.
Present alternative derived variables for use in sickle cell research. Suggest appropriate uses for these alternative derived variables. Conduct a standard analysis using mean steady state haematology, and repeat this analysis using a selection of alternative derived variables. Reference List 1. Serjeant GR, Serjeant BE, Forbes M, et, al.