Measuring the impact of Health Trainers Services on health and health inequalities: does the service's data collection and reporting system provide reliable information?

The Health Trainers Service is one of the few public health policies where a bespoke database-the Data Collection and Reporting System (DCRS)-was developed to monitor performance. We seek to understand the context within which local services and staff have used the DCRS and to consider how this might influence interpretation of collected data.In-depth case studies of six local services purposively sampled to represent the range of service provider arrangements, including detailed interviews with key stakeholders (n = 118).Capturing detailed information on activity with clients was alien to many health trainers' work practices. This related to technical challenges, but it also ran counter to beliefs as to how a 'lay' service would operate. Interviewees noted the inadequacy of the dataset to capture all client impacts; that is, it did not enable them to input information about issues a client living in a deprived neighbourhood might experience and seek help to address.The utility of the DCRS may be compromised both by incomplete ascertainment of activity and by incorrect data inputted by some Health Trainers. The DCRS is also underestimate the effectiveness of work health trainers have undertaken to address 'upstream' factors affecting client health.