Background: A commission was received to develop guidance on the organisation and delivery of diagnostic services across the National Health Service (NHS) in the UK. While well-established methodologies exist for development of clinical guidelines, health-service delivery is a relatively recent area in evidence-based guideline development and methodologies are still in their infancy.

Objectives: The commission was to cover all diagnostic-testing disciplines including endoscopy, imaging, physiology and pathology (including genetics) in all settings where NHS care is commissioned or provided. To inform scope development it was vital for the technical team to gather detailed background information on current service configurations across this extremely broad context. The aim was to identify variations in service provision and quality in order to inform priorities for evidenced-based guidance.

Methods: A mixed-methods approach was taken to gather information from a wide range of stakeholders, including health services commissioners and service organisers, healthcare professionals who carry out, receive or interpret results, and people who need to access services. Information was gathered through a stakeholder workshop, public consultation and a survey on current practice.

Results: Despite using a range of methods to access information, there remained a challenge in painting a comprehensive picture of the existing organisation of services across all diagnostic-testing settings. The majority of information received was disease- or situation-specific and not generalisable across the whole of the UK, or within any one diagnostic discipline.

Conclusions: This work highlighted the need for increased time and resources being available in the early stages of service guidance development. These guidelines require high levels of stakeholder engagement and special consideration should be given as to whether stakeholders are aware of, or can provide, context-specific evidence for service (re)organisation and (re)configuration. Any change from the current system may have a high resource impact and therefore needs to be supported by high-quality, applicable evidence.