Increasing uptake of National Health Service Health Checks in primary care: a pragmatic randomized controlled trial of enhanced invitation letters in Northamptonshire, England

Uptake of NHS Health Checks (NHSHCs) is sub-optimal. This study aimed to increase their uptake using behaviourally informed invitation letters. Patients registered with 6 general practices in Northamptonshire, England who were eligible for an NHSHC between 10 February 2014 and 31 January 2015 were randomized monthly, using a random number generator, to three trial arms: control (standard invitation), sunk costs (resources already allocated) and counterargument (against common barriers to attendance). The outcome measure was uptake of NHSHC by 12 weeks after 31 January. In total, 6331 patients were randomized. After exclusions, due to ineligibility for the NHSHC, data were analysed for N = 6313 patients: N = 2123 control; N = 2085 counterargument; N = 2105 sunk costs. Overall, 2364 (37.45%) patients attended an NHSHC. Both intervention letters increased uptake compared to control, by 5.46% using counterargument (adjusted odds ratio (AOR) 1.32, CI 1.162-1.51, p