This Week in BMJ | Editor's Choice | Press releases | Cover note

617 Meta-analysis and the meta-epidemiology of clinical research
C David Naylor

619 Food safety: from plough to plate
Fiona Godlee

620 Is human papillomavirus an infectious cause of non-cervical anogenital tract cancers?
Howard D Strickler, Mark H Schiffman

622 An amnesty for unpublished trials
Richard Smith, Ian Roberts

623 Multidrug resistance seen in plague case
Chronic illness high among manual workers
The end of the internal market?
"Quackery" outlawed in pharmacies
FDA to have more authority over food
WHO attacked for ignoring drug dumping
Genetic database to solve adoption scandal
US to ban pharmacy sale of many laxatives
Chronotherapy offers advantages
HIV home test kit banned in Germany
Karen Ignagni, Ms Managed Care, profiled

629 Bias in meta-analysis detected by a simple, graphical test
Matthias Egger, George Davey Smith, Martin Schneider, Christoph Minder

635 Impact of covert duplicate publication on meta-analysis: a case study
Martin R Tramer, D John M Reynolds, R Andrew Moore, Henry J McQuay

640 Publication bias: evidence of delayed publication in a cohort study of clinical research projects
Jerome M Stern, R John Simes

646 Prospective seroepidemiological study of role of human papillomavirus in non-cervical anogenital cancers
Tone Bjørge, Joakim Dillner, Tarja Anttila, Anders Engeland, Timo Hakulinen, Egil Jellum, Matti Lehtinen, Tapio Luostarinen, Jorma Paavonen, Eero Pukkala, Martin Sapp, John Schiller, Linda Youngman, Steinar Thoresen

650 Evaluation of fast track admission policy for children with sickle cell crises: questionnaire survey of parents' preferences
Caroline R Fertleman, Angela Gallagher, Mary A Rossiter

651 Usefulness of screening large numbers of contacts for tuberculosis: questionnaire based review
Helen Stoddart, Norman Noah

652 What is total purchasing?
Nicholas Mays, Nick Goodwin, Gwyn Bevan, Sally Wyke on behalf of the Total Purchasing National Evaluation Team

656 Fortnightly review: Management of patients with sickle cell disease
Sally C Davies, Lola Oni

661 ABC of mental health: Psychotropic drug treatment
Soumitra R Pathare, Carol Paton

665 Detecting the effects of thromboprophylaxis: the case of the rogue reviews
Mark Petticrew, Susan C Kennedy

668 Evaluating healthcare policies: the case of clinical audit
Joanne Lord, Peter Littlejohns

672 How to read a paper: Papers that summarise other papers (systematic reviews and meta-analyses)
Trisha Greenhalgh

675 Correction: Statistics for the non-statistician. I: Different types of data need different tests
Trisha Greenhalgh

676 Impact of postmenopausal hormone therapy on cardiovascular events and cancer
S Singleton and K Bailey; S Shah and L Rhodes; V Seagroatt; T Sundkvist; F Al-Azzawi and others; N F Col and others; E Hemminki

679 It is right to publicise recent advances in the media
G D Angelini and P Wilde

679 Finding of relation between epidural anaesthesia and long term backache remains valid
C MacArthur and others

679 Lowered risk of dying of heart attack with third generation pill may offset risk of dying of thromboembolism
M A Lewis and others

680 Treating shoulder complaints in general practice
G Symonds; C A Speed; B Orr; J C Winters

681 GPs and health authority believe that locality commissioning will improve services
R F Jankowski and others

682 Rapid opiate detoxification
D Rumball and J Williams; M M Laban and others

683 Ecchymoses may have been due to extracapsular haemorrhage from parathyroid adenoma
W P L Hellier and A McCombe

683 Inaccuracies in obituaries should not be ignored
E Wilson

683 Pharmaceutical industry is invited to respond to amnesty for unreported trials I Roberts

684 I S Bailey, P P Belliappa, R T Bevan, D R Dadge, L M Krishna, W J Patterson, C Rabindran, L J Samuels, V O G Smyth, F W A Turnbull, D R Wood, I L Woolf

686 An encounter with Reynard
Liam Farrell

686 The private life of systematic reviews
Ian Roberts, Gill Schierhout

The caring doctor is an oxymoron
Graeme M Mackenzie

688 Who can we blame?
Charles Essex

689 Evaluation Methods in Medical Informatics
Charles P Friedman, Jeremy C Wyatt John Faughnan

Cost-Effectiveness in Health and Medicine
M R Gold, J E Siegel, L B Russell, M C Weinstein Nick Freemantle

690

Editor's choice

Doctors' information: excessive, crummy, and bent

This theme issue of the BMJ considers the mess that is medical information.

Al Gore, vice president of the United States, has described the mess better than anybody. "Our current information policy," he said, "resembles the worst aspects of our old agricultural policy, which left grain rotting in thousands of storage files while people were starving. We have warehouses of unused information \`rotting' while critical questions are left unanswered and critical problems are left unresolved." We have much too much information of poor quality, too little that's good, and no effective way of sorting it out.

All this matters because most of what doctors do is of small benefit and potentially harmful. It's thus easy to confuse benefit and harm. When effects are small, large trials are needed to rule out the play of chance. But size cannot compensate for bias. Big numbers can mislead if data are biased - because investigators are keener on one outcome or because negative results are buried (p 640) and positive ones duplicated (p 635). Randomisation is needed to avoid bias.

Tribes of meta-analysts are busy trying to clear up the Augean stables of medical information. As Trish Greenhalgh describes (p 672), they pose clear and answerable questions, search for all relevant trials, discard those that don't meet specified quality criteria, and then draw conclusions from the relevant studies - perhaps by statistical amalgamation. They are much criticised for their pains, and many doctors remain sceptical of meta-analysis: "Put together lots of small rubbish studies and you have a big pile of rubbish studies, not an answer."

A collection of papers in this issue - summarised by David Naylor in an editorial (p 617) - look at several aspects of meta-analysis. Critics of meta-analyses ask whether they are good or bad. As our cover (explained on the contents page) suggests, the answer, as for any methodology, is that they are both. Editors and readers need to become more adept at telling good from bad. We must be sceptical about those that are put together from many small studies. We should question those that don't include an attempt to locate unpublished studies - because such studies are more likely than published ones to have negative results. (Our amnesty for unpublished trials (p 622) might help.) We should look for a "funnel plot," which will give us some help in determining whether there is likely to be bias in the studies included in the meta-analysis (p 629).

Finally, we should remember that the information that is drowning us is biased. Whatever technique we use to try to reach answers from the information - no matter whether it's a systematic review or grabbing the closest paper in the library - we cannot avoid that bias.