20 Aug 2009

Case Reports

A few colleagues asked me about case reports recently. The most common question is “Is this case worth reporting?”

Case report is the oldest form of medical literature. Clinicians described in details the patients they had saw, the treatment and subsequent outcome. When enough cases have been reported, generalizations can be made about the disease.

Fast forward to 21st century. With the explosion of information, it is rare to encounter diseases that few people have seen before (except new infectious diseases). Young colleagues often choose rare diseases with typical presentation. Though uncommon, these are usually diseases we meet once every few years. With a click on the keyboard, it is easy to find dozens of similar case reports already published. Saying “I have seen this too” is not very interesting.

Apart from describing new and rare diseases, case reports used to be platforms to discuss new medical treatments. However, without enough cases and controls, the outcome of a patient can hardly be attributed to the reported treatment. You can never prove or disprove if the patient would have the same or even better outcome if that treatment was not given. In the era of evidence-based medicine, the evidence on treatment efficacy provided by case reports is no better than expert opinion.

Does this mean that we should abandon case reports? No, writing case reports is excellent training. You learn not only writing skills, but also the ability to communicate medical information effectively with others.

Instead of describing rare conditions or novel treatments, I often encourage young people to watch out for uncommon presentations of common diseases. It can be as trivial as herpes zoster, or as dangerous as aortic dissection. Each encounter is an important lesson that everybody can learn.

P.S. Of course, whether a disease is rare depends on where you live. At one meeting, one colleague presented a case of intestinal tuberculosis. JL, a visitor from the Philippines, found that hilarious. She had a dozen of such cases in her ward at any time. To her, that presentation was no different from describing a typical case of COPD exacerbation.

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