Cluster effect to be considered - suggest design amend Ameet Bakhai, Barnet & Chase Farm NHS Trust, AMORE Health Ltd 11 May 2009 Dear Colleagues, This is an excellent innovation to be tested and a very well designed study. My main concern is that there will be a cluster effect that needs to be considered given that some patients at one centre and health care workers may overlap with each other and this is not an intervention that can be blinded. This will impact on resource and QoL impact. A more elegant design would be to enroll more centres and randomise centres to remove this effect to enable an unbiased impact on QoL and resource outcome. As you have stated - there is little doubt telephone strategies work but do they work due to the additional attention / scrutiny / manpower contact given or due to the mental attitudes of the patients being altered by the cognitive component? We would be happy to consider engaging in such a unique study. Thank you Ameet Bakhai, MBBS, FRCP Competing interests I work with various pharmaceutical and device companies in advisory capacities and lecturing capacities and participate in numerous clinical trials from design aspects to recruitment and steering committee roles.