Diagnostic Turnaround Time as a Determinant of Emergency Department Length of Stay and Admission Delay: A Systematic Literature Review (2019–2025)

Emergency Department (ED) crowding remains a persistent challenge for healthcare systems worldwide, with prolonged length of stay (LOS) contributing to compromised care quality, heightened clinical risks, and operational inefficiencies. Diagnostic turnaround time (TAT) has emerged as an important determinant of patient flow, potentially delaying clinical decisions and hospital admissions. This systematic review aimed to examine contemporary evidence published between 2022 and 2026 regarding the influence of diagnostic delays on ED LOS and subsequent hospital outcomes. Following PRISMA guidelines, a systematic search was conducted across PubMed, Scopus, and Web of Science, covering observational studies, predictive modeling research, and interventional studies addressing ED LOS, diagnostic processes, and admission delays. The findings indicated that diagnostic delays, particularly in laboratory testing and radiological examinations, were consistently associated with longer ED LOS and increased boarding time. Furthermore, interventions designed to streamline diagnostic pathways demonstrated measurable reductions in LOS and, in certain cases, mortality. These findings suggest that diagnostic TAT constitutes a modifiable operational factor with substantial implications for clinical outcomes and healthcare efficiency. Therefore, integrated, system-level strategies to optimize diagnostic workflows, improve coordination between clinical services, and accelerate decision-making are essential to enhancing patient flow, reducing unnecessary delays, and strengthening patient safety in emergency care settings.