Understanding and addressing the challenges of conducting quantitative evaluation at a local level: a worked example of the available approaches

OBJECTIVES: In the context of tightening fiscal budgets and increased commissioning responsibility, local decision-makers across the UK healthcare sector have found themselves in charge of the implementation and evaluation of a greater range of healthcare interventions and services. However, there is often little experience, guidance or funding available at a local level to ensure robust evaluations are conducted. In this paper, we evaluate the possible scenarios that could occur when seeking to conduct a quantitative evaluation of a new intervention, specifically with regards to the availability of evidence. DESIGN: We outline the full set of possible data scenarios that could occur if the decision-maker seeks to explore the impact of the launch of a new intervention on some relevant quantifiable outcomes. In each case we consider the implicit assumptions associated with conducting an evaluation, exploring possible situations where such scenarios may occur. We go on to apply the scenarios to a simulated dataset to explore how each scenario can result in different conclusions as to the effectiveness of the new intervention. RESULTS: We demonstrate that, across the full set of scenarios, differences in the scale of the estimated effectiveness of a new intervention and even the direction of effect are possible given different data availability and analytical approaches. CONCLUSIONS: When conducting quantitative evaluations of new interventions, the availability of data on the outcome of interest and the analytical approach can have profound effects on the conclusions of the evaluation. Although it will not always be possible to obtain a complete set of data and conduct extensive analysis, it is vital to understand the implications of the data used and consider the implicit assumptions made through its use.