Clinical Case Series

A Clinical Case Series is a Clinical Study that includes a group or series of case reports involving patients who were given similar treatment.

• AKA: Medical Case Series, Case Series.
• Context:
  • It usually carries out observations on a series of individuals, all receiving the same treatment (or intervention), before and after the treatment (or intervention) but with no control group.
  • It can range from being a Non-Consecutive Case Series to being a Consecutive Case Series.
• Example(s):
  • a Case Series of Children With 2019 Novel Coronavirus Infection,
  • …
• Counter-Example(s):
  • Case-Control Study,
  • Cohort Study,
  • Consecutive Controlled Case Series,
  • Randomized Controlled Trial,
  • Single-Case Experimental Design.
• See: Clinical Research, Medical Research, Institutional Review Board, Hypothesis Testing, Causality, Case-Only Studies, Genetic Epidemiology, Genotype.

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References

2021a

• (Wikipedia, 2021) ⇒ https://en.wikipedia.org/wiki/Case_series Retrieved:2021-11-21.
  • A case series (also known as a clinical series) is a type of medical research study that tracks subjects with a known exposure, such as patients who have received a similar treatment, or examines their medical records for exposure and outcome. Case series may be consecutive or non-consecutive, depending on whether all cases presenting to the reporting authors over a period were included, or only a selection. When information on more than three patients is included, the case series is considered to be a systematic investigation designed to contribute to generalizable knowledge (i.e., research), and therefore submission is required to an institutional review board (IRB). Case series usually contain demographic information about the patient(s), for example, age, gender, ethnic origin. etc. Case series have a descriptive study design; unlike studies that employ an analytic design (e.g. cohort studies, case-control studies or randomized controlled trials), case series do not, in themselves, involve hypothesis testing to look for evidence of cause and effect (though case-only analyses are sometimes performed in genetic epidemiology to investigate the association between an exposure and a genotype ). Case series are especially vulnerable to selection bias; for example, studies that report on a series of patients with a certain illness and/or a suspected linked exposure draw their patients from a particular population (such as a hospital or clinic) which may not appropriately represent the wider population. Internal validity of case series studies is usually very low, due to the lack of a comparator group exposed to the same array of intervening variables. For example, the effects seen may be wholly or partly due to intervening effects such as the placebo effect, Hawthorne effect, Rosenthal effect, time effects, practice effects or the natural history effect. Calculating the difference in effects between two treatment groups assumed to be exposed to a very similar array of such intervening effects allows the effects of these intervening variables to cancel out. Hence only the presence of a comparator group, which is not a feature of case-series studies, will allow a valid estimate of the true treatment effect.

2021b

• (Wikipedia, 2021) ⇒ https://en.wikipedia.org/wiki/Glossary_of_clinical_research Retrieved:2021-11-21.
  • Case series
    • A group or series of case reports involving patients who were given similar treatment. Reports of case series usually contain detailed information about the individual patients. This includes demographic information (for example, age, gender, ethnic origin) and information on diagnosis, treatment, response to treatment, and follow-up after treatment. (NCI)

2017

• (Mathes & Pieper, 2017) ⇒ Tim Mathes, and Dawid Pieper (2017) ["Clarifying the distinction between case series and cohort studies in systematic reviews of comparative studies: potential impact on body of evidence and workload"]. In: BMC Medical Research Methodology, 17(107).
  • QUOTE: Cohort study.
    • A study in which a defined group of people (the cohort) is followed over time, to examine associations between different interventions received and subsequent outcomes.
  • Case series.
    • Observations are made on a series of individuals, usually all receiving the same intervention, before and after an intervention but with no control group.
  • (...)
  • Cohort study: Patients are sampled on the basis of exposure. The occurrence of outcomes is assessed during a specified follow-up period.
  • Case series: Patients with a particular disease or disease-related outcome are sampled. Case series exist in 2 types:
    • 1. Sampling is based on a specific outcome and presence of a specific exposure.
    • 2. Selection is based only on a specific outcome, and data are collected on previous exposures. Cases are reported regardless of whether they have specific exposures. This type of case series can be seen as the case group from a case–control study.

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