Use of postcode to estimate individual risk of type 2 diabetes – is this valid?
I would like to make two points on the excellent attempt by Hippisley
-Cox and colleagues (1) at deriving a tool to estimate risk of developing
type 2 diabetes incorporating ethnicity and deprivation. The design of a
web based calculator (www.qdscore.org) available for use by patients for
self assessment of their risk is an interesting concept.
Firstly, I would like to request the authors to clarify the reason
for using the Townsend deprivation score. This has been replaced for a
while with the Index of Multiple Deprivation(2) which is a better and more
refined measure of deprivation and is widely used to assess and address
health inequalities in England and Wales.
Secondly, all variables used in the algorithm except the deprivation
score are measured at an individual level and therefore suitable for
individual risk assessment. Deprivation indices based on postcode are
useful to estimate population risk but can cause confusion when used to
predict individual risk. The same individual can change their risk by
simply moving from one post code to another. For example, a 43 year old
Indian female with family history of diabetes and BMI of 24kg/m2 could
reduce her risk from 5% to 3% by moving from London (SW3 2AS) to Suffolk
Risks for individuals should be based on personal indices of
socioeconomic status such as educational level or occupation or income
rather than postcode deprivation. It is therefore important that one or
more of such data are collected routinely to enable individual risk
1. Hippisley-Cox J, Coupland C, Robson J, Sheikh A, Brindle P.
Predicting risk of type 2 diabetes in England and Wales: prospective
derivation and validation of QDScore
Competing interests: No competing interests