ABSTRACT
When a disease is studied only in patients in a hospital, the symptomatic and morphologic features seen in those hospitalized patients may not accurately reflect the wild type disease which is prevalent in the population as a whole. This may result in an inaccurate picture of the disease. This is called ‘Berkson’s fallacy’ (he described it but did not commit it),1,2 and it may result in an increased chance of a positive or negative correlation being found where no or weak correlation actually exists. Since a description by Rokitansky in 1869,3 endometriosis has usually required surgery in a hospital or other health care facility for diagnosis. Thus, the risk has always silently existed that endometriosis could be spuriously linked to symptoms or other disease states due to the effects of Berkson’s fallacy acting unrecognized in hospitalized patients. Modern hindsight suggests that the decades-old effects of Berkson’s fallacy have led to misinterpretation of the symptoms of infertility and pain associated with endometriosis. This in turn has led to confusion and ineffective treatment which are the unfortunate modern hallmarks of the disease.
