People with the same disease may have symptoms in common, but they do not have identical symptoms, and they do not have identical responses. In setting up trials for orthodox drug treatments, this diversity has to be taken into account, but it creates conflicting demands:For the drug to be shown to be effective for a known set of symptoms, the cases used in the trial must be as similar as possible (the group must be homogeneous), but a completely homogeneous group is impossible to find;For the drug to have a general applicability for all those suffering the disease, the widest possible range of cases need to be included (the group needs to be general), but this increases variability in the responses and reduces the scientific value of the results.
There are several consequence of these conflicting demands:There can be no such thing as a perfect trial, since trials inevitably involve a compromise between homogeneity and generalisability.The results are only more or less scientific and only more or less applicable to people suffering the disease. Scientific accuracy may often be sacrificed for financial reasons. The individuality of response in patients means that drugs produce side effects, and these may not be identified during the trial.
As a result orthodox medicine recognises that controlled trial evidence alone cannot be relied on, but must be compared with evidence from clinical practice, a approach which forms the basis of evidence based medicine (EBM).
Evidence for the unreliability of medical RCTs was published in 2007. The table below is based on data obtained from an analysis of 1,016 systematic reviews of RCTs of conventional medicine (and therefore of many more than that number of RCTs in total). For comparison, information about trials of homeopathic treatment is included and there is a striking similarity of results. This suggests that the pattern of results relates to the method rather than to the type of medical approach used.