An Evidence-Based Resource for PainBMJ 1998; 317 doi: http://dx.doi.org/10.1136/bmj.317.7170.1460b (Published 21 November 1998) Cite this as: BMJ 1998;317:1460
Oxford University Press, £65, pp 272
ISBN 0 19 263048 2
Johnathan Cape £17.99, pp 292
ISBN 0224 06 0309
physicians' preference and the anecdote are dead—long live evidence based medicine. McQuay and Moore, from the University of Oxford's Pain Relief Unit, present the evidence to date of the effectiveness of various analgesic interventions in pain control by systematic review of all existing trials that have pain or adverse events as outcomes.
One of the most striking aspects of this book is what it does not contain. In particular, it highlights the paucity of trials investigating cancer pain. Pain is one of the most common and certainly the most feared symptom in malignant disease, and yet only 3% of all pain trials identified studied chronic cancer. The number of randomised controlled trials investigating acute and non-malignant pain published each year has increased dramatically since the mid-1970s.
Only high quality randomised controlled trials have been considered. The authors make no apology for this, believing it to be the only reliable way to estimate the true effect of an intervention. They have shown repeatedly throughout the book how small or lower quality studies are more likely to give positive results, often in direct contradiction to larger, more definitive studies. The results are presented as the number of patients needed to treat for one patient to achieve at least 50% pain relief along with, when possible, the number needed to treat for one patient to be harmed (suffer an adverse event). This concept is relevant to the individual patient and easy for clinicians to conceptualise.
The first part of the book presents a brief overview of the methodology behind systemic review, how the relevant trials were found, and how their quality was reviewed. Only eight of 80 existing systematic reviews of analgesic interventions satisfied McQuay and Moore's standards of quality.
Part two deals with acute (primarily postoperative) pain and reviews the evidence supporting the use of such common analgesic interventions as paracetamol, dextropropoxyphene, non-steroidal anti-inflammatory drugs, and transcutaneous electrical nerve stimulation. The summary chapter gives a “league table” of oral analgesics. The fact that non-steroidal anti-inflammatory drugs score so well (with respect to numbers needed to treat) while codeine and dihydrocodeine score so poorly will no doubt lead to some raised eyebrows and possibly lead to some change in clinical practice.
The section on chronic pain is disappointingly brief, reflecting the fact that there is remarkably little good evidence about the relative efficacy of drugs and their adverse effects after chronic dosing. The concluding chapter does not score analgesics as in part two but, instead, lists groups of drugs and interventions for which there is good evidence of effectiveness, for which this evidence if lacking, and for which there is good evidence of ineffectiveness. Several of the findings summarised here may make us question some aspects of the World Health Organisation's analgesic guidelines for chronic pain, which we have slavishly adhered to for so long.
One word of caution: readers should not presume that this excellent text gives all the answers. It is not a “cook book” for how to treat pain. Perhaps it should have been stressed more forcefully that evidence based medicine must always build on and reinforce clinical skills and clinical judgment and experience and that even this book will not provide a magic solution for every patient.