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OB - Trials RevisitedFrom: art fougner, md (evsono@pipeline.com)Tue Dec 22 12:11:11 1998
from the recent Lancet - Changing belief in obstetrics: impact of two multicentre randomised controlled trials Polly Jones, Richard Johanson, K Joanne Baldwin, Richard Lilford, Peter Jones Doctors may not know the results of relevant trials or apply them in everyday practice. Even when presented with results, their responses are not predictable. However rigorous the research, it must be assessed alongside other information before it can influence practice. De Vet and colleagues1 measured the informativeness of a paper by assessing the change in belief it induced. We investigated whether this method could be used after the publication of research studies to quantify long-term belief. We assessed two important high quality multicentre trials, CLASP2 and the Collaborative Eclampsia Trial3, that challenged perceived previously held views. The two papers had already been published and widely discussed; therefore, we were unable to measure previous beliefs in the absence of knowledge about the papers. We chose instead to ask clinicians directly about their beliefs before and after publication. We recorded the measurements of belief on a linear-analogue 10 cm scale ranging from certain disbeliever to enthusiastic believer. Questionnaires were sent to all 90 consultant obstetricians in the West Midlands, UK. We received 45 responses. To detect a change in belief, we compared before and after beliefs. The impact of the paper was expressed as a change ratio, which we calculated by dividing the level of belief after reading the paper, by the level of belief before reading it. For example, if the level of belief changed from 80% to 10%, the corresponding change ratio would be equal to (0·10/0·90)/(0·80/0·20)=0·09. A change ratio of 1 shows no impact. With a change ratio of less than 1, before belief is greater than after belief. Belief before and after publication of trials For the impact of the Collaborative Eclampsia Trial magnesium sulphate paper (figure) there was a strong change in belief away from being sceptical towards being enthusiastic (with only one score below the line of equality/no change). For the impact of the CLASP prophylactic aspirin paper (figure), most respondents showed a shift in belief towards being more sceptical (below the line of equality) but a few clinicians reported increases in belief. We have shown strong quantified changes in belief in the light of high quality evidence. The results are even more impressive when bias through the recall of the previous belief is taken into account. Our results confirm previously documented views,4 and suggest that clinicians can accurately recall previous beliefs. There are other ways of recording belief and our method does not produce a full Bayesian prior,5 but measurement can be made through simple approaches such as postal questionnaire. The Collaborative Eclampsia trial was unambiguous and led to change in belief. The less complete impact of the CLASP study did not convince enthusiasts. Concern about effects in certain subgroups and the importance of other outcomes may have influenced overall scores. Impact of research on belief can be simply measured. Whether changes in belief are translated into changes in practice, will require more study. We thank the consultants who contributed to this study and Nicola Leighton, Linda Lucking, and Claire Rigby for their assistance. 1 De Vet HCW, Kesssels AGH, Leffers P, Knipschild. A randomised trial about the perceived informativeness of new empirical evidence: does beta-carotene prevent (cervical) cancer. J Clin Epidemiol 1993; 46: 509-17. 2 CLASP Collaborative Group. A randomised trial of low-dose aspirin for the prevention and treatment of pre-eclampsia among 9364 pregnant women. Lancet 1994; 343: 619-29. 3 The Eclampsia Trial Collaborative Group. Which anticonvulsant for women with eclampsia: evidence from the Collaborative Eclampsia Trial. Lancet 1995; 345: 1455-63. 4 Hutton JD, James DK, Stirrat GM, Douglas KA, Redman CWG. Management of severe pre-eclampsia and eclampsia by UK consultants. Br J Obstet Gynaecol 1992; 99: 554-56. 5 Lilford R. Formal measurement of clinical uncertainty: prelude to a trial in peritoneal medicine. BMJ 1994; 308: 111-12. Academic Department of Obstetrics and Gynaecology, North Staffordshire Hospital, Newcastle-under-Lyme, Staffordshire ST4 6QG, UK (R Johanson; e-mail rbj@kogs.demon.co.uk) re- eclampsia - it's a given that the authors didn't poll Bernard. a Happy and a Merry to all Art
-- art fougner, md SonoScan/Genetic Sciences forest hills, ny evsono@pipeline.com
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