Article Text

Original research
How do the UK public interpret COVID-19 test results? Comparing the impact of official information about results and reliability used in the UK, USA and New Zealand: a randomised controlled trial
  1. Gabriel Recchia1,
  2. Claudia R Schneider1,2,
  3. Alexandra LJ Freeman1
  1. 1Winton Centre for Risk & Evidence Communication, Department of Pure Mathematics and Mathematical Statistics, University of Cambridge, Cambridge, UK
  2. 2Department of Psychology, University of Cambridge, Cambridge, UK
  1. Correspondence to Dr Gabriel Recchia; glr29{at}


Objectives To assess the effects of different official information on public interpretation of a personal COVID-19 PCR test result.

Design A 5×2 factorial, randomised, between-subjects experiment, comparing four wordings of information about the test result and a control arm of no additional information; for both positive and negative test results.

Setting Online experiment using recruitment platform Respondi.

Participants UK participants (n=1744, after a pilot of n=1657) quota-sampled to be proportional to the UK national population on age and sex.

Interventions Participants were given a hypothetical COVID-19 PCR test result for ‘John’ who was presented as having a 50% chance of having COVID-19 based on symptoms alone. Participants were randomised to receive either a positive or negative result for ‘John’, then randomised again to receive either no more information, or text information on the interpretation of COVID-19 test results copied in September 2020 from the public websites of the UK’s National Health Service, the USA’s Centers for Disease Control, New Zealand’s Ministry of Health or a modified version of the UK’s wording. Information identifying the source of the wording was removed.

Main outcome measures Participants were asked ‘What is your best guess as to the percent chance that John actually had COVID-19 at the time of his test, given his result?’; questions about their feelings of trustworthiness in the result, their perceptions of the quality of the underlying evidence and what action they felt ‘John’ should take in the light of his result.

Results Of those presented with a positive COVID-19 test result for ‘John’, the mean estimate of the probability that he had the virus was 73% (71.5%–74.5%); for those presented with a negative result, 38% (36.7%–40.0%). There was no main effect of information (wording) on these means. However, those participants given the official information from the UK website, which did not mention the possibility of false negatives or false positives, were more likely to give a categorical (100% or 0%) answer (UK: 68/343, 19.8% (15.9%–24.4%); control group: 42/356, 11.8% (8.8%–15.6%)); the reverse was true for those viewing the New Zealand (NZ) wording, which highlighted the uncertainties most explicitly (20/345: 5.8% (3.7%–8.8%)). Aggregated across test result (positive/negative), there was a main effect of wording (p<0.001) on beliefs about how ‘John’ should behave, with those seeing the NZ wording marginally more likely to agree that ‘John’ should continue to self-isolate than those viewing the control or the UK wording. The proportion of participants who felt that a symptomatic individual who tests negative definitely should not self-isolate was highest among those viewing the UK wording (31/178, 17.4% (12.5%–23.7%)), and lowest among those viewing the NZ wording (6/159, 3.8% (1.6%–8.2%)). Although the NZ wording was rated harder to understand, participants reacted to the uncertainties given in the text in the expected direction: there was a small main effect of wording on trust in the result (p=0.048), with people perceiving the test result as marginally less trustworthy after having read the NZ wording compared with the UK wording. Positive results were generally viewed as more trustworthy and as having higher quality of evidence than negative results (both p<0.001).

Conclusions The public’s default assessment of the face value of both the positive and negative test results (control group) indicate an awareness that test results are not perfectly accurate. Compared with other messaging tested, participants shown the UK’s 2020 wording about the interpretation of the test results appeared to interpret the results as more definitive than is warranted. Wording that acknowledges uncertainty can help people to have a more nuanced and realistic understanding of what a COVID-19 test result means, which supports decision making and behavioural response.

Preregistration and data repository Preregistration of pilot at, preregistration of main experiment at, data and code available online (

  • COVID-19
  • public health
  • health policy

Data availability statement

Data are available in a public, open access repository. All data and analytical code pertaining to this article are available at:

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Data availability statement

Data are available in a public, open access repository. All data and analytical code pertaining to this article are available at:

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  • GR and CRS contributed equally.

  • Contributors GR conceived of the experiment; GR, CRS and AF designed the questionnaire; GR and CRS carried out the quantitative analysis; AF analysed the free text; all authors wrote the manuscript.

  • Funding Funding was provided by the Winton Centre for Risk & Evidence Communication, which is funded from a donation from the David & Claudia Harding Foundation. The foundation played no role in the study.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Author note Gabriel Recchia & Claudia R. Schneider. The guarantors accept full responsibility for the work and/or the conduct of the study, had access to the data, and controlled the decision to publish. The guarantors affirm that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as pre-registered have been explained.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.