CA - Case Reports and Series

The critical appraisal of case series (the collection of a series of similar cases) and case reports (the report of a single or a few similar cases) is not well-detailed in the Evidence-based Medicine literature, but looking at these is sometimes the only published information available to you as a clinician looking for guidance.

If you are going to use case-reports and case series as evidence in answering your question, first make sure there's no better evidence out there. Case reports and case series are usually NOT systematically organized and planned - they are usually retrospective and are best used as hypothesis generating studies (where specific hypotheses can be later tested) or as evidence that a problem needs to be re-examined from a different perspective. As such they are important in the development of knowledge, but not necessarily the confirmation of knowledge. One of the first reports about AIDS was from a case series of Kaposi's sarcoma in gay men.

number of patients

the larger the sample, the better both for validity (to bolster the argument that the results were not "one-offs")

diagnostic categorization

the subjects should have similar case presentations as possible. including too many heterogeneous clinical presentations limits the ability for the researcher to prove that they are dealing with a common illness.

treatment protocol

if the study is about treating a known condition in a new way, then limiting the variety of treatment options/choices is important to build the evidence base that a treatment regimen works - so different dosages, lengths of treatment, etc. would weaken the story (unless the authors were able to demonstrate dose-response, etc.)

careful followup

there should be no, or minimal, loss to followup and the followup should be of sufficient time to allow for delayed outcomes and adverse events.

All or None results?

a special case - if, before the treatment exists, everyone died of the condition, then after the treatment, a significant number of people did not die - then that's convincing evidence that the treatment works. adverse events must be monitored closely, however, and careful followup should be done to ensure that death is not merely postponed for a short time.

adverse effects documentation?

For a case series, adverse events should be noted to ensure no untoward effects of the therapy, despite the zeal to publish the therapy's effect.

thoughtful discussion

the discussion should contain thoughts about the implications of the findings for clinical care, limitations of the study (especially in terms of subject demographics and baseline clinical presentations, and further research questions/directions to be explored.

appropriate clinical spectrum of patients

When applying this research to a specific clinical question, the subjects should look similar to the patient in the question.

demographic summary

there should be adequate description of the subjects in the study to facilitate comparison

A collection of case reports or small case series can be viewed as a body of data. In this case, attention should be paid to the similarity of patient presentation and treatment protocol specifically in order to make the combined results (analyzed qualitatively or quantitatively) meaningful.