At worst, they can cause useful treatments to be abandoned think of recent events concerning the MMR vaccine or potentially harmful procedures to be adopted remember past obstetric enthusiasm for routine fetal monitoring in pregnancy.
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.
Case series are at the bottom, contained in the rubric: 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.
At best, descriptions of case series act as catalysts for further investigation by methods that are more systematic.
Reports of case series will be given a warmer welcome, particularly if the circumstances are such that it would be unreasonable to demand a more systematic approach.
The investigators will need, however, to have been rigorous in their methodology and to have synthesized a useful amount of evidence. The main difficulties lie in coping with the diversity of study designs used by investigators, and the biases inherent in most observational studies.
Who can say whether the outcomes of the missing cases might have been very different? Reviews that conclude that there have been few studies, all of poor quality, and that further research is needed make poor reading.
For example, the effects seen may be wholly or partly due to intervening effects such as the placebo effect, Hawthorne effectRosenthal effecttime effects, practice effects or the natural history effect.
Another is that quirks in the way that unusual cases get referred make it hard to feel confident in generalizing from the experience of one centre.
At the same time, the condition that they describe must not be so rare that few readers of the journal will ever encounter a case. Even so, where they are of exceptional interest and written concisely, we may offer publication in the correspondence columns. But, despite this lowly position, there are many instances where valuable knowledge has come from someone taking the trouble to write up cases that are out of the ordinary.
Jump to navigation Jump to search 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. On the other hand, it must be admitted that descriptive studies have serious limitations.
Systematic reviews of observational studies are much harder to carry out and interpret than systematic reviews of randomized controlled trials.
N Engl J Med. Two modern classics are the reports of Pneumocystis carinii pneumonia and mucosal candidiasis in previously healthy homosexual men 1 and of hepatocellular adenomata in women taking oral contraceptives. Pneumocystis carinii pneumonia and mucosal candidiasis in previously healthy homosexual men: 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.
One is that retrospective reviews of case notes are rarely complete. Sometimes they construct diseases of doubtful validity but remarkable longevity.
A third, as Grimes and Schulz have pointed out, 3 is that without a comparison group, causal inferences about temporal associations need to be treated with deep suspicion.
No prizes for guessing that we are becoming unenthusiastic about reports of single cases. 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. So what should authors and readers expect from the QJM?Case series (CS) and case reports (CR) consist either of collections of reports on the diagnosis and treatment of individual patients, or of a report on a single patient.
There is another circumstance in which authors should write, and journals should publish, descriptive accounts of case series.
This is in rare conditions where population‐based studies or treatment trials are difficult or impossible to organize. Case Report or Series Case reports and series are a time-honored way to document stories of patients with rare or interesting diseases.
Some cases or interactions with patients lead to insights about important elements of care. Aug 21, · Case study and series Differences in aims A case study or case report is like a case series but it includes only one individual: • The aim is to describe a single and unusual incident or case.
A search for case series or case reports may reveal information that will assist in a diagnosis. However, for any reasonably well-known condition you should be able to get better evidence. Case series and case reports, since they use no control group with which to compare outcomes, have no statistical validity.
Journal of Medical Case Reports was the world’s first international, PubMed-listed medical journal devoted to publishing case reports from all clinical disciplines and was launched in The Case Report section of BioMed Central Research Notes was created and began publishing case reports inDownload