Description and nomenclature of 'outpatient' in medicine: A scoping review

The term "outpatient" refers to a patient attending hospital without overnight admission. Despite its importance in health service delivery, the term seems to be used inconsistently in the literature, hindering analysis and comparability.

To describe the use of outpatient in scientific and grey literature, identify patterns of incorrect usage, and propose an exploratory nomenclature.

We conducted a scoping review of scientific (Medline, 1952-2025) and grey literature (>2019). Eligible references included the term "outpatient" or described outpatient pathways within a hospital. The primary outcome was correct use of the formal definition. Multivariable regression explored patterns of incorrect use. A qualitative analysis informed the development of a proposed nomenclature.

Of 1624 scientific references, 984 were included; incorrect use occurred in 47%, as misuse, non-use, or mixed-use. Pattern of incorrect use were observed in relation to articles published before 2013, and without manual tags/MeSH terms. Grey literature showed similar patterns across countries and institutions. Inductive analysis yielded a four-category nomenclature: unscheduled, scheduled, coordinated, and supervised.

This study highlights the widespread incorrect use of the term "outpatient" across countries, journals, and institutions. Greater conceptual clarity and the use of a shared nomenclature may support more reliable descriptions of hospital activity, improve cross-country comparability, and inform evidence-based health policy analysis.