The enormous, even exponential, advance in the understanding of human genetics over the past three decades has so far yielded much less improvement in clinical results than was once hoped. It has proved more difficult than anticipated to translate biological knowledge into clinical benefit.
This is not, of course, to say that there have been no benefits at all from the advances in genetic understanding, particularly in such fields as prenatal counselling. Another superficially promising field is that of pharmacogenetics, that is to say the prediction of responses to medicaments according to the patients’ genetic type. This is very important, for hitherto it has proved difficult to predict whether a patient will respond positively or negatively to a given treatment, and whether he or she needs a higher or a lower dose to produce a desired effect.
The latter is particularly important in the case of treatment with anticoagulants (blood-thinners) because a therapeutic dose is usually so close to a dangerous dose. If we could predict who needs what dose rather than, as at present, proceed essentially by trial and error, it would be of great advantage to patients who need anticoagulation. They would receive the benefit of anticoagulation – fewer heart attacks and strokes – without the risks of complications such as cerebral and other bleeds.
Three trials of attempts to tailor doses of anticoagulants according to the patients’ genetic type have been published in a recent edition of the New England Journal of Medicine. The authors compared prescription of anticoagulants by the normal methods with determination by genetic type. The results of the three trials were contradictory.