The two quotations below come from people who argued vehemently over the role and importance of EBM yet agreed on the importance of the individual within the system.
"Evidence-based medicine is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patient." .
"Managers and trialists may be happy for treatments to work on average; patients expect their doctors to do better than that." .
This underlines the importance of looking at information from the point of view of the individual patient. In acute pain, patients have been shown generally to obtain pain relief that is either very good or poor, but the average of responses to analgesics is at a point where there are few, if any, patients . It is commonly understood that not every patient with a particular condition benefits from treatments known to work (on average). Patients may discontinue therapy because of adverse events as well as lack of efficacy, especially in chronic conditions. A clinical trial may tell us that 50% of patients have pain relief with drug, compared with 20% with placebo, and we applaud a good NNT of 3.3. Yet that obscures the fact that half the patients do not have pain relief but may have adverse effects.
A classic example demonstrating how different we all are is provided by a trial in which depressed patients were randomized to one of three antidepressants which were, on average, the same . Patients initially randomized to one treatment frequently changed to another. By 9 months only 44% were still taking the treatment to which they had been randomized. Some (about 15%) were lost to follow-up after baseline or when on any of the randomized treatments. Others either switched to another antidepressant or stopped treatment because of adverse effects or lack of efficacy, again without any difference between the three antidepressants. Each was taken by about the same proportion, on average, just different patients to those initially randomized. Patients and their doctors found the balance of effect and absence of adverse events that was right for them, and almost 70% had a good outcome over the 9 months of the trial.
The degree of variability between individuals in their physiologic response to drugs is remarkable, and best exemplified by a study of 50 healthy young volunteers who received rofecoxib 25 mg, celecoxib 200 mg or placebo in randomized order, and who underwent a series of tests . There was considerable variability between individuals in cyclo-oxygenase 2 inhibition achieved, and in selectivity, for both of the drugs. Variation between individuals was 50 to several hundred-fold in activity in different in vitro tests following a single dose. Differences were associated with genetic polymorphisms and other factors were involved in the variability observed. Similarly, a range of polymorphisms in genes coding for enzymes metabolizing morphine, opioid receptors, and blood-brain barrier transport of morphine by drug receptors all contribute to considerable variability between individuals . A number of mechanisms can influence individual responses to analgesics .
There are important practical implications following these findings. They obviously relate particularly to the potential harm of limited formularies, but also challenge how we use average results from trials in making decisions about individual patients.
Was this article helpful?