| Summary: | Children are vulnerable to adverse drug reactions (ADRs) but have been under-represented in studies which have addressed their incidence and prevention. The aim of my thesis was to undertake a prospective study of ADR-related hospital admissions. The first step involved the development of the methodology by undertaking a prospective observational pilot study assessing all unplanned admissions over a 2 week period. There were 19 admissions to the main hospital wards related to an ADR, giving an estimated ADR incidence of 4%. Among the methodological considerations assessed in the study was the definition of what constitutes an admission (whether to include patients admitted to the Accident & Emergency observation ward), the feasibility of the data collection methods, and an assessment of the feasibility of managing the workload between three investigators. ADR causality assessment in the pilot study was undertaken using the validated Naranjo tool. However, this was found to be lacking in sensitivity, with underestimation of the likelihood of an ADR. A causality assessment tool (CAT) that would overcome some of these issues, while at the same time making it as easy, or easier, to use than the Naranjo tool was formulated by an expert focus group. We undertook a comparison of the new Liverpool CAT with the Naranjo tool using seven assessors. This showed that the Liverpool CAT assigned the full range of causality categories and showed better inter-rater reliability than Naranjo. ADRs causing paediatric hospital admission were subsequently studied over a one year period. There were 247 ADRs in 240/8345 patients admitted acutely to the hospital, giving an estimated ADR admission incidence of 2.9% (95% CI 2.5, 3.3). There were no deaths attributable to an ADR. 120/249 (48.2%) ADRs resulted from treatment for malignancies. The origin of prescription for causative drugs was assessed; prescriptions originating in the community accounted for 44/249 (17.7%) of ADRs with the remainder from hospital. Assessment of the avoidability of the ADR cases using the Liverpool CAT showed that 22.1% (95% CI 17%, 28%) of the reactions were either ‘definitely’ or ‘possibly’ avoidable. Few studies in the literature have reported specific avoidability outcomes, which is important to prioritise interventional strategies to reduce the burden of ADRs. ADRs in children are an important public health problem. Most of those serious enough to require hospital admission are due to hospital-based prescribing, of which just over a fifth may be avoidable. Strategies to reduce the burden of ill-health from these ADRs are needed.
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