Health professionals' and service users' interpretation of screening test results: experimental study

doi:10.1136/bmj.38884.663102.AE

BMJ 2006;333:284 (5 August), doi:10.1136/bmj.38884.663102.AE (published 13 July 2006)

Research

Health professionals' and service users' interpretation of screening test results: experimental study

Ros Bramwell, senior lecturer¹, Helen West, research student¹, Peter Salmon, professor¹

¹ Division of Clinical Psychology, University of Liverpool, Liverpool L69 3GB

Correspondence to: R Bramwell rosb{at}liv.ac.uk

Abstract

Objective To investigate the accuracy of interpretation of probabilisticscreening information by different stakeholder groups and whetherpresentation as frequencies improves accuracy.

Design Between participants experimental design; participantsresponded to screening information embedded in a scenario.

Setting Regional maternity service and national conferencesand training days.

Participants 43 pregnant women attending their first antenatalappointment in a regional maternity service; 40 companions accompanyingthe women to their appointments; 42 midwives; 41 obstetricians.Participation rates were 56%, 48%, 89%, and 71% respectively.

Measures Participants estimated the probability that a positivescreening test result meant that a baby actually had Down'ssyndrome on the basis of all the relevant information, whichwas presented in a scenario. They were randomly assigned toscenarios that presented the information in percentage (n =86) or frequency (n = 83) format. They also gave basic demographicinformation and rated their confidence in their estimate.

Results Most responses (86%) were incorrect. Obstetricians gavesignificantly more correct answers (although still only 43%)than either midwives (0%) or pregnant women (9%). Overall, theproportion of correct answers was higher for presentation asfrequencies (24%) than for presentation as percentages (6%),but further analysis showed that this difference occurred onlyin responses from obstetricians. Many health professionals wereconfident in their incorrect responses.

Conclusions Most stakeholders in pregnancy screening draw incorrectinferences from probabilistic information, and health professionalsneed to be aware of the difficulties that both they and theirpatients have with such information. Moreover, they should beaware that different people make different mistakes and thatways of conveying information that help some people will nothelp others.

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This article has been cited by other articles:

(2006). Interpreting Probabilistic Test Results Is Difficult for Most. JWatch General 2006: 5-5 [Full text]
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Rapid Responses:

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