Pragmatic Case Series — Real-World Observational Case Description
Pragmatic Case Series Study · Also known as: real-world case series, pragmatic observational case series, practice-based case series
A pragmatic case series is an observational study that documents consecutive or purposively selected patients receiving a clinical intervention or presenting with a condition under routine, real-world practice conditions — without randomization, a control group, or the highly controlled eligibility criteria characteristic of explanatory trials. It is used to describe treatment patterns, outcomes, and adverse events as they occur in everyday clinical settings.
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When to use it
Use a pragmatic case series when you need to document the real-world experience with a procedure, drug, device, or rare condition in a clinical setting and randomization or a control group is not feasible or ethical. It is well suited to early safety surveillance, describing treatment patterns for rare diseases, generating hypotheses for future controlled studies, and reporting outcomes in under-represented populations excluded from trials. Do not use it when causal conclusions about treatment efficacy are required — without a comparator group and with broad eligibility, confounding cannot be controlled and efficacy claims are not supportable. It is also inappropriate as a replacement for a properly powered cohort study or trial when those designs are feasible.
Strengths & limitations
- Reflects real-world clinical practice, making findings immediately relevant to practicing clinicians.
- Feasible even when randomization is unethical, impractical, or the condition is rare.
- Captures diverse patient populations including those with comorbidities typically excluded from explanatory trials.
- Low organizational burden compared to randomized trials — leverages routinely collected clinical data.
- Useful for early safety signals, hypothesis generation, and documenting treatment patterns in novel settings.
- No comparator group means causal inference about efficacy is not possible; observed outcomes may reflect natural disease course rather than the intervention.
- Selection bias is difficult to assess when consecutive enrolment is not strictly maintained or documentation is incomplete.
- Confounding by indication — sicker or different patients may receive different treatments, distorting outcome comparisons even descriptively.
- Generalizability is limited to the practice setting and patient mix studied; findings may not transfer to other contexts.
Frequently asked
What distinguishes a pragmatic case series from a standard case series?
The core design is the same — consecutive or systematically identified patients, no control group, descriptive outcomes. The pragmatic label signals that the study is set in routine clinical care with broad eligibility criteria, that data come from real-world sources rather than research-specific data collection, and that the explicit goal is to inform practical clinical decisions rather than to test a narrowly defined hypothesis under controlled conditions.
Can I calculate incidence or risk from a pragmatic case series?
Only if you have a clearly defined denominator — the total population from which the cases arose. A case series alone does not provide a denominator, so incidence rates cannot be reliably calculated. If the data source (e.g., a practice registry) provides a defined patient population, you may be able to estimate event rates, but this requires careful documentation of the denominator and follow-up time.
What reporting guideline should I follow?
The PROCESS (Preferred Reporting Of CasESeries in Surgery) guideline is the most widely adopted standard for surgical and procedural case series. For pharmacological or non-surgical contexts, relevant EQUATOR Network guidelines or the CARE guideline (for individual case reports, extended to small series) should be consulted. Adherence to a guideline substantially improves the transparency and interpretability of the report.
How many patients do I need for a pragmatic case series?
There is no formal minimum, but a series typically includes at least 10 patients to provide meaningful descriptive statistics and to distinguish the study from a single case report. The appropriate number depends on the rarity of the condition, the frequency of the outcomes of interest, and the clinical question. Formal sample size calculations are not standard for descriptive case series, though they may be applied if specific outcome frequencies are to be estimated with a target precision.
Is a pragmatic case series considered high-quality evidence?
Case series occupy the lower tiers of the evidence hierarchy (typically Level 4 in systems such as the Oxford CEBM levels) because of the absence of a control group and susceptibility to confounding and selection bias. However, in clinical contexts where higher-quality evidence is unavailable — particularly for rare diseases or novel interventions — a well-conducted pragmatic case series provides valuable real-world data that informs clinical practice and regulatory decision-making.
Sources
- Schwartz, D., & Lellouch, J. (1967). Explanatory and pragmatic attitudes in therapeutical trials. Journal of Chronic Diseases, 20(8), 637–648. DOI: 10.1016/0021-9681(67)90041-0 ↗
- van Walraven, C., & Davis, D. A. (2007). Case series and case report. In: Knottnerus JA, Buntinx F (eds). The Evidence Base of Clinical Diagnosis. 2nd ed. BMJ Books. link ↗
How to cite this page
ScholarGate. (2026, June 3). Pragmatic Case Series Study. ScholarGate. https://scholargate.app/en/epidemiology/pragmatic-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
- Cohort StudyEpidemiology↔ compare
- Pragmatic randomized clinical trialEpidemiology↔ compare
- Prospective Case SeriesEpidemiology↔ compare
- Retrospective Case SeriesEpidemiology↔ compare