Process evaluation

To understand if treatments such as drugs or procedures affect outcomes like symptoms, quality of life and survival, medical researchers conduct studies comparing outcomes of patients that receive a treatment, to outcomes of patients that do not. However, because many treatments are complex in that they involve multiple parts or people, it can be difficult to understand the meaning of study results because of local differences influencing the way the treatment being studied was introduced and delivered.

A process evaluation is a study that occurs alongside a main study. It enables understanding of factors that influence how a treatment was introduced and maintained during a study, and how much of the treatment was delivered as planned. We will conduct a process evaluation of a multicentre study looking at whether antibiotics given to critically ill adults during admission to an intensive care unit (ICU) to prevent rather than treat an infection reduces death, antibiotic use and antibiotic resistance rates. The study is the Selective Decontamination of the Digestive tract in Intensive Care Unit patients study.

We will conduct surveys, interviews and audits, and observe practice in ICUs taking part in the trial to understand:

• how the treatment was introduced at each ICU and maintained over time
• if the treatment was delivered as planned
• what this information can tell us to understand the results of the main trial.

Our process evaluation will enable us to understand better if preventive antibiotics save lives and reduce antibiotic usage, and their impact on antibiotic resistance. It also will give us information about whether we could expect the same findings if we introduced the intervention into other ICUs after the study and how best to do this.