Observations The Art of Risk Communication

HIV screening: helping clinicians make sense of test results to patients

BMJ 2013; 347 doi: https://doi.org/10.1136/bmj.f5151 (Published 21 August 2013) Cite this as: BMJ 2013;347:f5151
  1. Gerd Gigerenzer, director
  1. 1Harding Centre for Risk Literacy and Centre for Adaptive Behaviour and Cognition, Max Planck Institute for Human Development, Berlin
  1. gigerenzer{at}mpib-berlin.mpg.de

Natural frequencies foster insight and should become part of the training of every medical student and HIV counsellor

In April 2013 the US Preventive Services Task Force recommended that clinicians screen for HIV infection in people aged 15-65 years, revising its earlier position to screen only people at increased risk and pregnant women.1 The proposal elicited discussion about the benefits and harms of antiretroviral treatment, the ethics of testing without people’s explicit consent, and much else, but it neglected one crucial issue: risk literacy among clinicians.

When my colleagues and I tested 20 professional HIV counsellors, 10 wrongly asserted that false positive test results never occurred, and eight confused the test’s sensitivity (the proportion of people with HIV who actually test positive for it) with its positive predictive value (the proportion of people who test positive who actually have HIV), with only two understanding what a positive test result meant.2 In a replication of this study in progress we see little improvement.

Does innumeracy among clinicians matter? No systematic studies of effects on patients exist—just anecdotal reports of people with false positive test results engaging in unprotected …

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