Multicenter Case Series — Multi-Site Descriptive Clinical Study
Multicenter Case Series Study · Also known as: multi-site case series, multicentre case series, collaborative case series, multi-institutional case series
A multicenter case series is an observational descriptive study in which consecutive or selected patients sharing a defined clinical condition are enrolled and followed at two or more independent clinical sites. By pooling cases across institutions, researchers achieve larger sample sizes and greater demographic and clinical diversity than a single-center series permits, enabling more reliable description of disease presentation, management patterns, and outcomes for rare or uncommon conditions.
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When to use it
Use a multicenter case series when the condition or event of interest is too rare for a single center to accumulate adequate numbers within a feasible timeframe, and the research goal is description rather than causal inference. It is especially appropriate for rare diseases, unusual complications, novel surgical procedures, or emerging pathogens where establishing incidence, clinical spectrum, or management patterns is the priority. The design is also useful as a hypothesis-generating step before planning a controlled study. Do not use it when a control or comparison group is needed to estimate treatment efficacy or causal effects — a cohort study or randomized trial is required for those questions. Avoid if case ascertainment across sites cannot be standardized, because site-specific selection biases will distort the pooled description.
Strengths & limitations
- Enables study of rare conditions by aggregating cases that no single site could collect alone.
- Captures greater clinical and demographic diversity than a single-center series, improving external validity.
- Generates detailed descriptive data on disease presentation, management variation, and short-term outcomes.
- Can be executed relatively quickly in retrospective form using existing medical records.
- Serves as a strong basis for hypothesis generation and for powering future controlled studies.
- No comparison group, so causal inference about exposures or treatments is not possible.
- Susceptible to selection bias if case ascertainment differs across sites or if not all eligible cases are captured.
- Heterogeneity in clinical practice, recording conventions, and follow-up duration across sites can complicate pooled analysis.
- Results describe the studied case series and may not generalize beyond the participating centers and their patient populations.
- Retrospective versions rely on medical record quality, which varies by site and era.
Frequently asked
How is a multicenter case series different from a multicenter cohort study?
Both enroll patients at multiple sites, but a cohort study follows a defined population over time and typically includes a comparison group (exposed vs. unexposed) to estimate risk or rate ratios. A case series describes a group of patients with a shared condition without a comparison group, making causal inference impossible. The case series is a purely descriptive design; the cohort study is analytic.
How many sites and cases are needed?
There is no universal rule, but the number of cases needed depends on the rarity of the condition and the descriptive precision required. For rare diseases, even 20–50 pooled cases across 3–5 sites may be informative. For more common conditions the bar is higher. Practical considerations — logistics of coordination, available infrastructure, and funding — usually determine the number of participating sites.
Should ethics approval be obtained at each site separately?
Yes, in most jurisdictions each participating site requires local ethics or IRB review, though many institutions now support central IRB reliance agreements that streamline the process. The coordinating center typically prepares a master protocol that each site submits to its own committee. Investigators should plan for the time and administrative burden of multi-site ethics approval early in the study design phase.
What reporting guideline should I follow?
The PROCESS (Preferred Reporting Of CasE Series in Surgery) guideline — published in 2016 and updated in 2020 — provides a checklist specifically designed for case series and is widely endorsed by surgical journals. For non-surgical contexts, adapted STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) elements are often recommended. Always check the target journal's author instructions for preferred reporting standards.
Can a multicenter case series support regulatory submissions?
Regulatory agencies (e.g., FDA, EMA) may accept multicenter case series data as supportive evidence for rare-disease drug approvals or expanded indications, particularly under orphan-disease or accelerated-approval pathways. However, they are generally considered lower-quality evidence than controlled studies and are rarely sufficient alone; they are most valuable when randomized evidence is ethically or practically impossible to obtain.
Sources
- Dekkers, O. M., Vandenbroucke, J. P., Cevallos, M., Renehan, A. G., Altman, D. G., & Egger, M. (2012). COSMOS-E: Guidance on conducting systematic reviews and meta-analyses of observational studies of etiology and prognosis. PLoS Medicine, 9(2), e1001175. link ↗
- Matthews, J. N. S. (2006). Introduction to Randomized Controlled Clinical Trials (2nd ed.). Chapman and Hall/CRC. ISBN: 978-1584886242
How to cite this page
ScholarGate. (2026, June 3). Multicenter Case Series Study. ScholarGate. https://scholargate.app/en/epidemiology/multicenter-case-series
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
- Case seriesEpidemiology↔ compare
- Multicenter Case-Control StudyEpidemiology↔ compare
- Multicenter cohort studyEpidemiology↔ compare
- Multicenter Randomized Clinical TrialEpidemiology↔ compare
- Retrospective Case SeriesEpidemiology↔ compare