Introduction: Rapid point-of-care diagnostic tests (POCTs) have been widely advocated to improve the use of antibiotics and medical resources. The extent of the adoption of POCTs for the clinical management of acute childhood infections in European countries and the determinants of adoption are unclear. Aim and Objectives: The aim of this thesis is to address evidence gaps about the factors which contribute to the adoption of POCTs for the clinical management of acute childhood infections in European settings. Objectives:- Objective 1: To estimate the variability in the availability and use of POCTs for the clinical management of acute childhood infections across European countries. - Objective 2: To explore the determinants of this variability across European countries. - Objective 3: To generate an in-depth understanding of the factors that contribute to high- versus low-level availability of C-reactive protein (CRP) POCTs in primary care settings in two countries with similar primary healthcare systems, and to explore whether the tests are used in children. - Objective 4: To generate an in-depth understanding of the factors that contribute to the different levels of availability and use of CRP POCTs in hospitals in these two countries. Methods: A mixed methods approach was used to meet these objectives: - Objective 1: Quantitative cross-sectional survey of European primary care and hospital paediatricians. - Objective 2: Multilevel logistic regression analyses to assess the contribution of explanatory factors to the adoption of POCTs at two levels: 1) workplace and clinician level, and 2) country of work level. - Objective 3: Comparative qualitative case studies at primary care level, based on documents analysis and in-depth interviews of stakeholders in the Netherlands and England. The study was informed by the non-adoption, abandonment, scale-up, spread and sustainability (NASSS) framework. - Objective 4: Comparative qualitative case studies at hospital level, based on documents analysis and in-depth interviews of stakeholders in the same countries. The study was also informed by the NASSS framework. Results: - Objective 1: 2342 paediatricians from 29 European countries took part in the cross-sectional survey. The availability and use of the nine POCTs included in the survey vary substantially across Europe. - Objective 2: The country of work better predicts the availability and use of POCTs than workplace or healthcare workers characteristics. - Objective 3: 65 documents were identified, and 21 interviews were conducted. CRP POCTs are more widely available in primary care in the Netherlands than in England mainly because of the interplay between early adopters and factors at the macro level of health systems. These factors include the existence of a fee-for-service reimbursement scheme, the better integration of health services, and the lower funding constraints in the Netherlands. In both countries CRP POCTs are used less frequently in children than in adults because of the perceived uncertainty regarding the accuracy and effectiveness of using these tests in children, the lack of guidelines, and the perceived invasiveness of finger pricking.- Objective 4: 41 documents were identified, and 46 interviews were conducted. The main contributors to the higher adoption of CRP POCTs in hospitals in the Netherlands lie at the micro and macro levels. Most hospital healthcare workers in the Netherlands are familiar with CRP POCTs and trust the tests because they are widely used in primary care. Moreover, hospital funding is more limited in England. Most hospitals in the Netherlands and England have not adopted CRP POCTs because the hospital laboratory is able to provide laboratory-based CRP results in a few hours at a lower cost. Conclusion: The adoption of POCTs is a complex phenomenon even though the technology itself appears to be relatively simple and easy to use. The adoption of POCTs for the management of acute childhood infections varies substantially across Europe. Factors at the macro level of health systems are more influential overall in determining the adoption of POCTs. Differences in reimbursement mechanisms, the integration of health services, overall expenditure on healthcare, and healthcare workers’ trust are the main contributors towards the greater adoption of CRP POCTs in the Netherlands compared to England. The specific factors that contribute to the adoption of CRP POCTs and other POCTs in other countries with different health systems structures and processes may be different. Should these POCTs and future POCTs be implemented, understanding these factors would be essential for informing their implementation.