Development of the ASSIGN score
The ASSIGN score was developed in the summer of 2006 by Professor Hugh Tunstall-Pedoe and Professor Mark Woodward based at the University of Dundee, Scotland, working with the SIGN (Scottish Intercollegiate Guidelines Network) group on cardiovascular risk estimation and with a particular contribution from Dr Peter Brindle. ASSIGN is a cardiovascular risk score. The name is derived from "ASSessing cardiovascular risk using SIGN" (see below) guidelines to ASSIGN preventive treatment.
Derivation of the score is described in a paper published in Heart online in November 2006 and in print February 2007. The coefficients used in its calculation appear in appendix to the paper.
By convention (following Framingham scoring, and expert recommendations) the presumption is that anyone whose ASSIGN cardiovascular risk score is 20 or more is ‘high risk’ and a candidate for preventive treatment, and anyone with a score below that does not normally qualify. The score should be applied within the context of SIGN Guideline 97 or a similar protocol. Note the cutpoint for the score, now 20, was different in the past, and may possibly change in the future.
The development
The score arose out of an invitation to Professor Hugh Tunstall-Pedoe (University of Dundee) to join a SIGN group on cardiovascular risk estimation. The group was concerned through the participation of Professor Graham Watt of Glasgow University with the effect on cardiovascular risk of social deprivation which he had been studying in the Midspan cohort from west central Scotland.
The issue was developed further by Professor Tunstall-Pedoe with Professor Mark Woodward on a Scotland-wide basis using the SHHEC (see below) study of representative men and women recruited by the Dundee team across Scotland from 1984 to 1995.
Importance of social deprivation
The study published in Heart in September 2005 and in print in 2006 showed a large gradient in coronary risk in Scottish men and women related to their social status (defined by SIMD-see below) but inadequately explained by conventional risk factors, so not allowed for in the Framingham score (see below).
This meant that traditional cardiovascular scores, such as Framingham, would result in the socially deprived being allocated less preventive treatment in relation to their future risk than the socially privileged, unless the effect of social deprivation was allowed for in some other way.
Professor Hugh Tunstall-Pedoe and Professor Mark Woodward updated the SHHEC database and extended the study to cardiovascular disease as the endpoint, rather than just coronary heart disease. Opinion was divided in the SIGN group as to whether the Framingham score should be adjusted by ‘tweaking it’ to take account of social deprivation, or whether a new score would be needed.
This was best answered by deriving a score incorporating social deprivation along with classic risk factors (family history was also added at the suggestion of Dr Peter Brindle) and seeing whether it could then be emulated by ‘tweaking’ the Framingham score.
The ASSIGN score
The new score was ASSIGN. It proved difficult to ‘tweak’ Framingham to take account of social deprivation for several reasons, although Framingham cardiovascular scores and ASSIGN scores were highly correlated when tested in the SHHEC study.
ASSIGN was therefore adopted by SIGN after it had been shown that results of scoring against Framingham cardiovascular score (see paper) were very similar in most individuals, ASSIGN scores being slightly lower. A positive family history and a high score for social deprivation lifted the ASSIGN score towards or above that from Framingham cardiovascular score and made it fairer in a mixed population. The use of family history would also bring out the ethnic susceptibility to premature cardiovascular disease, although ethnicity is not specifically catered for.
Note the JBS2 'cardiovascular score' used in England combines a Framingham coronary and stroke score to give a lower reading than ASSIGN, as does QRISK (see later). ASSIGN is therefore intermediate in its calibration between the derived JBS2 score and the published Framingham cardiovascular score.
The ASSIGN score has been validated by comparison with the Framingham cardiovascular score in its own host population and by multiple iteration to overcome the effect of testing in its own database. Its discrimination has been compared favourably to other scores in its own SHHEC database, as above, but also in the 2003 Scottish Health Survey (unpublished), QRESEARCH and more recently the THIN databases (see paper and editorial). (See SIGN Guideline 97).