Abstracts

Communicating risk

Those marketing commercial DNA tests often suggest that knowing your risk of a disease will prevent certain risky behaviours. A case in point is Crohn’s disease and smoking. Those who have the genotype that predisposes to Crohn’s may reduce their risk of developing the disease by never smoking or stopping smoking. Hollands et al. used a randomised controlled trial to test the hypothesis that people who know their risk of developing Crohn’s would stop smoking to reduce this risk.

The trial looked at 497 smokers who were first-degree relatives of those with Crohn’s disease – 209/251 people had DNA testing and 217/246 had standard risk assessment. The primary outcome was smoking cessation for 24 hours or longer, assessed at 6 months.

The intervention was communication of risk assessment for Crohn’s disease by postal booklet based on family history of the disease and smoking status alone, or with additional DNA analysis for the NOD2 genotype. Participants were then telephoned by a National Health Service Stop Smoking counsellor to review the booklet and deliver brief standard smoking cessation intervention. Calls were tape recorded and a random subsample was selected to assess fidelity to the clinical protocol.

The proportion of participants who stopped smoking for 24 hours or longer did not differ between arms: 35% (73/209) in the DNA arm versus 36% (78/217) in the non-DNA arm. The proportion who made a quit attempt within the DNA arm did not differ between those who were told they had mutations putting them at increased risk (36%), those told they had none (35%), and those in the non-DNA arm (36%).

Among relatives of patients with Crohn’s disease, feedback of DNA-based risk assessments does not motivate behaviour change to reduce risk any more or less than standard risk assessment. These findings accord with those across a range of populations and behaviours. They do not support the promulgation of commercial DNA-based tests nor the search for gene variants that confer increased risk of common complex diseases on the basis that they effectively motivate health-related behaviour change.

Hollands GJ, et al. BMJ 2012;345 [http://dx.doi.org/10.1136/bmj.e4708] (published 20 July 2012).