부산대학교 도서관

Imaging is the foundation of almost all clinical pathways and an increasingly influential tool for both the diagnosis and treatment of a wide spectrum of conditions. This thesis describes three individual studies, one randomised controlled trial (RCT) and two observational studies, performed in the context of an organisation-wide transformation initiative called TOHETI (Transforming Outcomes and Health Economics Through Imaging) at Guy’s and St Thomas’ NHS Foundation Trust (GSTT). All three studies converged in the evaluation of the effectiveness and cost-effectiveness associated with the innovative use of advanced imaging in the context of clinical pathways in the National Health Service (NHS). The economics associated with the utilisation of advanced imaging has changed over time due to the combined effect of growth in demand and technological developments that have led to advanced imaging becoming more accurate, accessible and less costly. However, there is still limited evidence around the cost and health economic implications associated with the use of advanced imaging. A systematic review conducted by the student assessed the challenges and methodological approaches used in the economic evaluation of diagnostic tests and constituted the foundation for the study design and statistical analyses employed in all three empirical studies. The first study, a single-centre RCT, assessed the immediate use of Magnetic Resonance Imaging (MRI) in the management of suspected scaphoid fractures in the emergency department (ED) at GSTT. This study followed a published systematic review conducted by the student that highlighted the lack of both empirical economic evidence and appropriate economic modelling evidence on the immediate use of advanced imaging in the management of suspected scaphoid fractures. One-hundred and thirty six participants entered the study and were randomised to receive either the intervention with immediate MRI or follow routine care, which did not consider the use of MRI in the acute setting. This study was truly innovative as, to our knowledge, MRI is not considered in the context of acute care. The primary outcome was to estimate the cost implications from the healthcare payer perspective. Secondary outcomes included wider costs, cost-effectiveness and cost-utility (cost per quality-adjusted life years), diagnostic accuracy, clinical findings, time taken to reach a definitive diagnosis and patient satisfaction. Generalised linear models (GLM) were undertaken to estimate the main effect of group in all cost analyses. Based on intention-to-treat principles, the use of immediate MRI led to cost savings and, given the available data, there was a 96% to 100% probability of being cost-effective at conventional willingness-to-pay thresholds in the UK. The second study, a single-centre pragmatic observational study, evaluated the utilisation of GP direct access to MRI compared to referral to neurology services for patients with chronic headache. Despite the benign nature of most headaches, headache management is associated with high healthcare utilisation, accounting to up to one third of neurologist appointments. The study’s underlying hypothesis was that the early use of an advanced and accurate diagnostic tool (in this case MRI) would reassure both patients and GPs that no serious underlying cause (particularly brain tumour) was present. This would in turn reduce the headache burden and NHS resource use associated with the patient’s subsequent management. For this purpose, a total of two-hundred and forty nine patients were recruited for both groups (MRI and neurology groups) as per standard care. The primary outcome was to estimate the cost implications from the healthcare payer perspective. Secondary outcomes considered further cost and cost-effectiveness analyses, accessibility to care, time off-work and patient satisfaction. Cost analyses were conducted using GLMs and, given the study’s non-randomised design, adjusted for potential imbalances at baseline. Based on intention-to-treat principles, direct referral to brain MRI from primary care led to cost savings, quicker access to care but lower patient satisfaction levels when compared with referral to neurology services. The third study, a single-centre pragmatic observational study, evaluated the utilisation of Computed Tomography Colonography (CTC) compared to Optical Colonoscopy (OC) as the first line colonic investigation in the assessment of patients with low to intermediate risk of colorectal cancer (CRC). CRC is one of the leading causes of mortality and morbidity worldwide, with the UK presenting five-year survival rates significantly lower compared to other countries. Recent clinical guidelines aimed to increase early diagnosis of CRC by lowering the threshold for colonic investigations. However, this led to a substantial increase in colonic investigations, particularly OC, the diagnostic reference test for CRC, which remains technically difficult and resource intensive. This study evaluated the substitution of CTC as a first-line colonic investigation for patients deemed at low to intermediate risk of CRC. The underlying rationale was that CTC, a non-invasive and less costly colonic investigation, would be able to rule-out CRC or large polyps, thereby avoiding the need for invasive OC tests. Moreover, this would release much needed OC resources to test patients with known CRC or at a higher risk of CRC. The primary outcome was to estimate the cost implications from the healthcare payer perspective. Secondary outcomes considered cost-effectiveness and cost-utility, accessibility to care and patient satisfaction. Based on intention-to-treat principles, the use of CTC generated cost savings and presented a probability of 84%-91% of being cost-effective at conventional willingness-to-pay thresholds. The use of CTC also improved access to care, with no impact in patient satisfaction. The role of observed data versus economic modelling is discussed taking into consideration published economic literature and its implications to interventions in the medical imaging field. The findings from a priori decision-analytical models were then compared to the empirical evidence retrieved from the three studies. Additionally, the student investigated whether the two methodological approaches would have led to different decisions from policy makers and ultimately affect the adoption of medical imaging technologies. The last chapter completes the thesis with an overarching discussion of the main findings from model and real-world studies and their implications in the wider context of real-world NHS clinical practice. The implementation plans for the three different clinical pathways are detailed with the aim of bridging the gap between the clinical and economic evidence and the actual delivery of care across the NHS.