PREVENTABLE SINGLE AND CONSECUTIVE DOSE OMISSIONS IN HOSPITAL SETTINGS: A MULTI-PHASE MIXED-METHODS STUDY INVESTIGATING THEIR NATURE, PREVALENCE, CAUSES, AND PREDICTORS ACROSS ALL MEDICATIONS, WITH A SPECIFIC FOCUS ON HIGH-RISK MEDICATION

Abstract

Omitted prescribed medication doses remain among the most frequently reported medication administration errors in hospitals. Although their overall prevalence is well documented, many studies fail to distinguish preventable causes—such as supply or communication issues—from non-preventable ones, including clinical decisions or patient refusals. This lack of clarity contributes to inconsistent definitions and reporting of preventable omissions, limiting the development of effective, targeted safety interventions. Moreover, existing research often focuses on specific high-risk medications (HRMs) or single omissions, overlooking broader HRM categories and the potentially dangerous pattern of consecutive omissions. This thesis investigates prevalence, causes, and behavioural influences in hospital settings, with particular emphasis on HRMs, using a three-phase mixed-methods approach. Phase One comprises two systematic reviews exploring the nature, prevalence, and causes of preventable medication dose omissions—one encompassing all medications and the other focused specifically on HRMs. Systematic searches across eight databases inform a meta-analysis of prevalence estimates and a thematic analysis guided by Reason’s Accident Causation Model. The findings show that, although electronic prescribing and medicines administration (EPMA) systems are associated with lower omission rates compared to paper-based systems, variation in reported prevalence persists due to inconsistent definitions and methodologies, limiting comparability. Preventable omissions are often linked to failures by healthcare professionals (HCPs) to provide, administer, or document

medications, frequently driven by workload pressures and environmental distractions. Some omissions related to patient factors or administration route barriers are misclassified as non-preventable. Only one low-quality study reports the prevalence of consecutive omissions within a single HRM group. Phase Two involves a qualitative study based on semi-structured interviews with HCPs, using purposive and snowball sampling across two large hospitals within a West Midlands Trust. Drawing on Reason’s model, the analysis identifies wideranging organisational and environmental factors that contribute to unsafe acts leading to both single and consecutive preventable dose omissions. Using the Theoretical Domains Framework (TDF), 11 of the 14 behavioural domains are identified. These domains reflect both system-level and individual-level influences—such as the design and use of electronic systems, workload demands, and professional behaviours— that serve as barriers and contributing factors to preventable dose omissions across all medications, including HRMs. Phase Three presents a retrospective analysis of electronic medication administration records (eMAR) from a large National Health Service (NHS) Trust, focusing on a wide range of HRMs that have the potential to cause patient harm if delayed or omitted. Omissions were defined as doses administered more than 90 minutes after the scheduled time or not given at all, with a documented reason, in line with international standards. The preventability of omissions was determined based on documented reasons, following the definition provided by the National Coordinating Council for Medication Error Reporting and Prevention (NCC MERP). Based on the 90-minute threshold, frequent dosing intervals and

intravenous routes were associated with preventable omissions. First-dose omissions were also linked to preventable omissions, while weekend timing predicted consecutive omissions with documented reasons, emphasising key risk periods for these events. Overall, this research addresses the prevalence, causes, and nature of preventable omitted doses across all hospital medications, particularly HRMs. It identifies predictors and barriers to safe administration through a mixed-methods analysis. The findings emphasise the need to enhance electronic systems, deliver targeted staff training, and address workload and resource challenges in order to reduce preventable omissions and ensure the safe, timely administration of medications.