Individuals who receive a negative lateral flow coronavirus test result may misunderstand it as meaning ‘no risk of infectiousness’, giving false reassurance. This experiment tested the impact of adding information to negative test result messages about residual risk and the need to continue protective behaviours.
4 (residual risk) × 2 (post-test result behaviours) between-subjects design.
Online.
1200 adults from a representative UK sample recruited via Prolific (12–15 March 2021).
Participants were randomly allocated to one of eight messages. Residual risk messages were: (1) ‘Your coronavirus test result is negative’ (control); (2) message 1 plus ‘It’s likely you were not infectious when the test was done’ (current NHS Test & Trace (T&T); (3) message 2 plus ‘But there is still a chance you may be infectious’ (elaborated NHS T&T); and (4) message 3 plus infographic depicting residual risk (elaborated NHS T&T+infographic). Each message contained either no additional information or information about the need to continue following guidelines and protective behaviours.
(1) Proportion understanding residual risk of infectiousness and (2) likelihood of engaging in protective behaviours (scales 1–7).
The control message decreased understanding relative to the current NHS T&T message: 54% versus 71% (Adjusted Odds Ratio (AOR)=0.56 95% CI 0.34 to 0.95, p=0.030). Understanding increased with the elaborated NHS T&T (89%; AOR=3.25 95% CI 1.64 to 6.42, p=0.001) and elaborated NHS T&T+infographic (91%; AOR=5.16 95% CI 2.47 to 10.82, p<0.001) compared with current NHS T&T message. Likelihood of engaging in protective behaviours was unaffected by information (AOR=1.11 95% CI 0.69 to 1.80, χ2(1)=0.18, p=0.669), being high (
A considerable proportion of participants misunderstood the residual risk following a negative test result. The addition of a single sentence (‘But there is still a chance you may be infectious’) to current NHS T&T wording increased understanding of residual risk.
OSF:
A well-powered, representative sample of UK adults imagined taking part in asymptomatic lateral flow coronavirus testing.
Participants were randomly allocated to read one of eight test-negative result messages.
Information currently delivered by NHS Test and Trace was compared with a control message and two intervention messages.
Expectations of engaging in protective behaviours were measured during a period of national lockdown.
As part of the global effort to reduce the transmission of coronavirus (COVID-19), asymptomatic testing via rapid antigen tests such as lateral flow devices (LFDs) has become widespread.
The extent to which people understand the residual risk of infection after a negative asymptomatic COVID-19 test result is not known. Research in cancer screening suggests that 43% of people believe they definitely do not have cervical cancer following a normal smear test result.
Importantly, the way in which negative test results are communicated can affect understanding and behaviour. For example, communicating that there is still a risk of cervical cancer after a negative screening result increases understanding that having cancer is unlikely or very unlikely compared with communicating that the residual risk is lower than for the average person (OR 5.46).
Test result messages also offer an opportunity to communicate the need to continue adhering to protective behaviours after a negative result, which might not be immediately clear if individuals are given a negative result but told that they could still be infectious. Unambiguous behavioural instructions and guidelines in COVID-19 messaging are encouraged by The British Psychological Society and can provide the knowledge and capability people need to engage in protective behaviours.
At the time the study was conducted, the NHS Test and Trace (T&T) negative result messaging communicated some residual risk which was positively framed (see
‘Your coronavirus test result is negative’.
This means you should continue to follow all government guidance to reduce transmission of the virus. You must stay at home. You must not leave or be outside of your home except where necessary.
Remember – ‘Hands. Face. Space’.
Hands – wash your hands regularly and for at least 20 seconds.
Face – wear a face covering in indoor settings where social distancing may be difficult and where you will come into contact with people you do not normally meet.
Space – stay 2 m apart from people you do not live with where possible, or 1 m with extra precautions in place (such as wearing face coverings).
Given the dearth of research examining the understanding of residual risk and behaviours following a negative COVID-19 LFD test, we conducted an online experiment examining the impact of communicating about residual risk and protective behaviours following a negative test result. The protocol was preregistered on Open Science Framework (
Hypothesis 1: understanding of residual risk is (A) increased by adding existing NHS T&T messaging compared with no information about residual risk (control) and (B) increased further by adding an elaborated message and an infographic.
Hypothesis 2: expectations to follow coronavirus guidelines are higher when messages contain information about the need for continued engagement in protective behaviours.
Participants were randomly allocated to a message in a 4 (residual risk) × 2 (post-test result behaviours) between-subjects design (see
A cross-stratified quota sample of 1207 UK adults representative of the UK population based on sex, age and ethnicity was recruited via the online platform Prolific (
The power analyses conducted with G*Power (V.3.1) indicated that a sample of 1095 was needed to test the hypotheses. For hypothesis 1, given the lack of prior data, a power analysis for a logistic regression could not be conducted and was based on a χ2 test instead. A sample of 547 can detect a difference between two groups with a small effect size (
Participants imagined they had taken a lateral flow test and received one of eight messages in a 4 (residual risk) × 2 (post-test result behaviour) factorial design (see
The message also contained either none or some information about the need to maintain adherence to protective behaviours following a negative test result, as listed on UK government guidance under national lockdown in March 2021.
Primary outcome measures were understanding of residual risk and behavioural expectations to follow COVID-19 guidelines after receiving a hypothetical negative test result (see
Behavioural expectations to follow COVID-19 guidelines were measured with specific protective behaviour questions and a general question. Six protective behaviours were measured with a seven-point scale question: ‘After receiving this test result, how likely is it that you would engage in the following behaviours because of coronavirus?’ (behaviours: social distancing, hand washing, wearing a face covering, avoiding meeting others, working from home, avoiding public transport; 1: very unlikely to 7: very likely), taken from a previous study.
Secondary outcome measures were confidence in understanding, perceived test accuracy and testing uptake expectations (see
Participants were asked about their previous testing experience, including the last time they took a coronavirus test and what type of test it was (see
Participants were recruited via Prolific and then directed to the study on Qualtrics. They were asked to imagine they had taken a lateral flow test as part of a local mass asymptomatic testing programme, similar to those taking place in the UK.
Patients and/or the public were not involved in the development of the study due to the rapid nature of this research. However, the experiment was piloted with 16 participants to ensure it ran smoothly and that there were no errors. Those who took part in the pilot were able to provide feedback to researchers on the study.
Preregistered analyses were conducted using Stata (V.15) with a significance level of p<0.05. To test hypothesis 1, a binomial logistic regression was conducted with residual risk, post-test result behaviour and an interaction term as predictors of understanding (coded as correct: ‘I am most likely not infectious with coronavirus’ or incorrect: all other responses). Group 2 (current NHS T&T) was used as the reference category for the residual risk predictor. Age, gender, ethnicity, education, location and numeracy were added to the model as covariates. Expected engagement in specific behaviours was negatively skewed and remained in violation of the assumption of normality following logarithmic transformation. The preplanned 4 (residual risk) × 2 (post-test result behaviour) between-subjects ANOVA on specific protective behaviours was therefore unsuitable and an ordinal regression was conducted to test hypothesis 2. Other analyses reported are exploratory. The dataset is publicly available.
Of the 1207 participants who completed the study, seven (0.6%) failed the attention check and were excluded from the analysis. A breakdown of the demographic characteristics of the remaining 1200 participants can be found in
Participant demographic characteristics
Demographic characteristic | n | % |
Gender | ||
Male | 582 | 48.50 |
Female | 615 | 51.20 |
Non-binary | 1 | 0.10 |
Prefer not to say | 2 | 0.20 |
Age (years) | ||
18–24 | 127 | 10.60 |
25–34 | 205 | 17.10 |
35–44 | 206 | 17.20 |
45–54 | 217 | 18.10 |
55–64 | 274 | 22.80 |
65+ | 171 | 14.30 |
Education | ||
GCSE or equivalent | 221 | 18.40 |
A level or equivalent | 298 | 24.80 |
Undergraduate degree | 482 | 40.20 |
Postgraduate degree | 199 | 16.60 |
Ethnicity | ||
White – British | 906 | 75.50 |
White – other | 113 | 9.40 |
Asian | 98 | 8.20 |
Black | 41 | 3.40 |
Mixed | 32 | 2.70 |
Other | 10 | 0.90 |
UK region | ||
Northern Ireland/Scotland/Wales | 162 | 13.40 |
England – South | 316 | 26.30 |
England – London | 155 | 12.90 |
England – Midlands | 268 | 22.30 |
England – North | 299 | 24.90 |
Testing experience | ||
Yes – PCR | 235 | 19.60 |
Yes – Lateral flow test | 281 | 23.40 |
Yes – other (eg, antibody) | 33 | 2.80 |
Yes – don’t know | 44 | 3.70 |
None | 607 | 50.60 |
GCSE, General Certificate of Secondary Education.
Understanding varied by residual risk message as outlined in hypothesis 1 (see
Percentage of participants with a correct understanding of residual risk by residual risk experimental group. Error bars represent 95% CIs. Significance levels are based on the logistic regression in
Primary and secondary outcomes (% (n); mean (SD)) by experimental group
Residual risk | Post-test result behaviours | |||||
Control (n=300) | NHS T&T (n=298) | Elaborated (n=302) | Infographic (n=300) | None (n=602) | Included (n=598) | |
Understanding | ||||||
I am not infectious | 45.3 (n=136) | 28.2 (n=84) | 9.6 (n=29) | 7.7 (n=23) | 19.6 (n=118) | 25.8 (n=154) |
I am most likely not infectious* | 54.3 (n=163) | 71.1 (n=212) | 88.7 (n=268) | 90.7 (n=272) | 79.7 (n=480) | 72.7 (n=435) |
I am most likely infectious | 0 (n=0) | 0.3 (n=1) | 1.3 (n=4) | 0.7 (n=2) | 0.5 (n=3) | 0.7 (n=4) |
I am infectious | 0.3 (n=1) | 0.3 (n=1) | 0.3 (n=1) | 1.0 (n=3) | 0.2%(n=1) | 0.8 (n=5) |
Specific behaviours | ||||||
Average | 6.40 (0.9) | 6.46 (0.8) | 6.42 (0.9) | 6.33 (1.1) | 6.39 (0.9) | 6.41 (0.9) |
Social distancing | 6.52 (1.0) | 6.55 (1.0) | 6.53 (1.0) | 6.46 (1.2) | 6.53 (1.0) | 6.50 (1.1) |
Hand washing | 6.45 (1.0) | 6.50 (1.0) | 6.46 (1.1) | 6.41 (1.2) | 6.48 (1.1) | 6.44 (1.1) |
Face covering | 6.70 (0.8) | 6.71 (0.9) | 6.71 (0.9) | 6.55 (1.3) | 6.70 (0.9) | 6.63 (1.1) |
Avoid meeting others | 6.20 (1.3) | 6.21 (1.3) | 6.15 (1.3) | 6.00 (1.5) | 6.09 (1.3) | 6.18 (1.3) |
Work from home | 6.19 (1.5) | 6.32 (1.4) | 6.24 (1.4) | 6.21 (1.4) | 6.20 (1.5) | 6.28 (1.4) |
Avoid public transport | 6.28 (1.4) | 6.47 (1.2) | 6.44 (1.2) | 6.34 (1.3) | 6.35 (1.3) | 6.43 (1.2) |
Expectations to follow guidelines | 4.23 (0.9) | 4.18 (0.8) | 4.25 (0.9) | 4.32 (0.9) | 4.19 (0.8) | 4.30 (0.8) |
Confidence in understanding | 4.17 (0.8) | 4.35 (0.8) | 4.23 (0.8) | 4.32 (0.8) | 4.24 (0.8) | 4.29 (0.8) |
Perceived testing accuracy | 5.71 (1.1) | 5.71 (1.1) | 5.61 (1.1) | 5.95 (1.0) | 5.75 (1.1) | 5.74 (1.1) |
Future testing expectations | 5.90 (1.6) | 5.92 (1.6) | 5.88 (1.6) | 5.99 (1.6) | 5.90 (1.6) | 5.95 (1.6) |
*Correct understanding of residual risk. Confidence is on a five-point scale and other continuous variables on a seven-point scale.
NHS, National Health Service; T&T, Test and Trace.
Logistic regression predicting correct understanding of residual risk
AOR | 95% CI | Wald | P value | |
Intercept | 0.61 | 0.29 to 1.31 | 1.58 | 0.209 |
Residual risk | ||||
Control | 0.56 | 0.34 to 0.95 | 4.70 | 0.030 |
NHS T&T (reference) | ||||
Elaborated T&T | 3.25 | 1.64 to 6.42 | 11.50 | 0.001 |
Elaborated T&T+infographic | 5.16 | 2.47 to 10.82 | 18.94 | |
Post-test result behaviours | ||||
Without (reference) | ||||
With | 0.81 | 0.48 to 1.36 | 0.65 | 0.421 |
Residual risk* post-test result behaviours | ||||
NHS T&T * with (reference) | ||||
Control * with | 0.65 | 0.32 to 1.33 | 1.38 | 0.240 |
Elaborated T&T * with | 0.95 | 0.38 to 2.37 | 0.01 | 0.907 |
Elaborated T&T+infographic * with | 0.77 | 0.29 to 2.04 | 0.27 | 0.605 |
Gender† | ||||
Male (reference) | ||||
Female | 1.06 | 0.78 to 1.43 | 0.13 | 0.716 |
Age (years) | ||||
18–24 | 1.76 | 0.93 to 3.33 | 3.07 | 0.080 |
25–34 | 1.45 | 0.85 to 2.46 | 1.87 | 0.172 |
35–44 | 1.56 | 0.91 to 2.65 | 2.66 | 0.103 |
45–54 | 1.74 | 1.03 to 2.91 | 4.35 | 0.037 |
55–64 | 1.68 | 1.04 to 2.73 | 4.41 | 0.036 |
65+ (reference) | ||||
Education | ||||
GCSE or equivalent (reference) | ||||
A-level or equivalent | 1.82 | 1.18 to 2.80 | 7.27 | 0.007 |
Undergraduate | 2.73 | 1.82 to 4.11 | 23.29 | |
Postgraduate | 4.95 | 2.85 to 8.61 | 32.12 | |
Ethnicity | ||||
White British (reference) | ||||
White other | 0.81 | 0.47 to 1.41 | 0.53 | 0.465 |
Asian | 0.61 | 0.34 to 1.09 | 2.83 | 0.093 |
Black | 0.33 | 0.15 to 0.71 | 7.94 | 0.005 |
Mixed | 0.36 | 0.15 to 0.91 | 4.70 | 0.030 |
Other | 0.64 | 0.12 to 3.54 | 0.26 | 0.613 |
Location | ||||
London (reference) | ||||
Northern Ireland | 1.12 | 0.27 to 4.57 | 0.02 | 0.876 |
Scotland | 0.82 | 0.41 to 1.63 | 0.33 | 0.567 |
Wales | 0.62 | 0.28 to 1.40 | 1.31 | 0.252 |
South England | 1.08 | 0.63 to 1.83 | 0.08 | 0.784 |
Midlands | 1.46 | 0.84 to 2.54 | 1.76 | 0.185 |
North England | 0.86 | 0.51 to 1.46 | 0.32 | 0.574 |
Numeracy | ||||
Incorrect (reference) | ||||
Correct | 1.69 | 1.17 to 2.45 | 7.85 | 0.005 |
*Significant p values are shown in bold.
†To ensure meaningful comparisons between genders, participants who reported their gender as ‘non-binary’ (n=1) or ‘prefer not to say’ (n=2) were excluded from the logistic regression analysis given low numbers in each group. When included in the analysis, their understanding of residual risk was not significantly different from the reference category (male) nor did this alter the significance or direction of the other effects or analyses.
As planned, we explored whether residual risk messages affected confidence in understanding among those who were correct (76.3%) to assess the effectiveness of messages beyond understanding. Residual risk information affected confidence (
The variable measuring expectations to engage in protective behaviours remained negatively skewed after logarithmic transformations making the preplanned ANOVA unsuitable. An ordinal regression was conducted to explore the influence of information about residual risk, post-test result behaviours and their interaction on expected engagement in protective behaviours, which was rounded to the nearest whole value and reverse scored to allow easier interpretation of the model.
Communicating the need to maintain protective behaviours following a negative test result did not significantly increase expected engagement in protective behaviours (AOR=1.11 95% CI 0.69 to 1.80, χ2(1)=0.18, p=0.669), which does not support hypothesis 2. Neither the level of residual risk information nor the interaction between residual risk information and post-test result behaviours had a significant effect on expected engagement in protective behaviours (see
An ordinal regression was also conducted to explore the influence of the predictors on expectations to follow guidelines compared with before receiving a negative result. This variable was clustered around the centre of the scale; 82% of participants selected option 4 – the same as before. Communicating the need to maintain protective behaviours following a negative test result did not significantly increase expectations to follow guidelines (AOR=1.24 95% CI 0.66 to 2.29, χ2(1)=0.45, p=0.502). Neither the level of residual risk information nor the interaction between residual risk and post-test result behaviours had a significant effect on expected engagement in protective behaviours (see
Perceived accuracy of lateral flow tests (see
Expectations to engage in asymptomatic lateral flow testing in the future (see
We explored whether those who had a correct understanding (n=915) were more likely to engage in protective behaviours compared with those who reported that there was no residual risk (n=272), bearing in mind participants were not randomised to each group. Those with a correct understanding did not have higher expected engagement in protective behaviours (
Enhanced communication of residual risk information in negative asymptomatic coronavirus test results improved understanding of residual risk, without evidence that it decreased the perceived accuracy of LFDs or testing uptake expectations. The elaborated NHS T&T message was better understood than the current NHS T&T message (89% vs 71% correct), which itself was more effective than giving no residual risk information (54% correct), in support of hypothesis 1. The elaborated NHS T&T message added residual risk information that was negatively framed (‘But there is still a chance you may be infectious’) to the current NHS T&T message, which was positively framed (‘It’s likely you were not infectious when the test was done’). This study therefore echoes previous findings on negatively framed communications of residual risk,
Adding an infographic with an icon array of residual risk did not significantly improve understanding relative to the elaborated NHS T&T message. This may be due to a ceiling effect given that the elaborated NHS T&T message increased understanding to nearly 90%. Although it contrasts with previous findings on the effectiveness of infographics,
Importantly, a substantial proportion of participants had an incorrect understanding of the residual risk inherent in a test-negative result after reading the negative result message without any residual risk information (46%) or the current message used by NHS T&T (29%). This emphasises the importance of revising existing messaging and wider communications to better address misconceptions among the general public. Lower levels of understanding were also evidenced among certain demographic groups. Understanding was lower as education level and numeracy decreased, in those aged 65+ years compared with those aged 45–64 years and in groups self-classifying as black and mixed ethnicity compared with white British. This mirrors findings in other risk communication trials, where higher understanding is associated with higher education,
This study provides the first experimental evidence that some misunderstand there to be no residual risk of infectiousness following a negative asymptomatic COVID-19 test result, while demonstrating the effectiveness of simple, low-cost interventions to increase understanding. Implementing these interventions would be a valuable step in ensuring that the implications of asymptomatic LFD testing are more often understood by the public.
The study has several limitations. First, participants were responding to a hypothetical test result. The interventions would benefit from being tested in a real world setting to check that the increase in understanding is maintained. Second, expectations of engaging in protective behaviours were high. This could have been due to national lockdown restrictions being in place at the time, as in previous studies.
It is possible that the correct response to the measure of residual risk understanding was made salient to participants by the linguistic similarity between the information presented in three of the residual risk conditions (‘It’s likely you were not infectious’) and the wording of the correct item (‘“I am most likely not infectious’). However, significant differences in understanding were observed between conditions where this wording was used (NHS T&T, Elaborated condition, Infographic condition). This suggests that participant responses were not exclusively driven by recognition of wording similarity and that the addition of a single sentence (‘But there is still a chance you may be infectious’) was sufficient in improving relative understanding of residual risk. Future studies could investigate the influence of wording similarity by exploring alternative measures of residual risk understanding.
The results of this study suggest that adding one sentence to a pre-existing single sentence can increase understanding of the meaning of a negative test result. These findings merit implementation with an evaluation to confirm whether understanding influences behaviour in a real-world setting. However, stronger messages may be needed in contexts where residual risk of infectiousness is higher than in asymptomatic community testing programmes. Messages that include only negatively framed residual risk information could be more effective than the combined positive and negative framing used in this study.
The study also suggests that there was a considerable level of misunderstanding (46%) among participants who received no residual risk information, with the majority believing that a negative LFT result means they are not infectious. It is likely that these misconceptions also exist in situations where residual risk information is absent, such as when individuals conduct an LFT at home and read their result directly from the test device. Residual risk information should be clearly communicated in information booklets that accompany home test kits and policymakers should consider how this can be disseminated beyond the testing environment to improve understanding among those less likely to read or receive test result messages.
The effects of education, numeracy and ethnicity on understanding of residual risk were consistent with prior studies on risk communication,
The authors would like to thank the Winton Centre for Risk and Evidence Communication for designing the infographic, Henry Potts for statistical advice and providing comments on the manuscript, Louise Smith for providing comments on the manuscript and Ross Harris for providing statistical advice.
@E_Batteux
EB contributed to conceptualising and designing the study, completed data collection and analysis and drafted the manuscript. SB contributed to conceptualising and designing the study, assisted with data collection and analysis, and contributed to and approved the final manuscript. LFJ, HC, NG, RA and DW contributed to conceptualising and designing the study, and contributed to and approved the final manuscript. TM framed the broad research question, contributed to conceptualising and designing the study, contributed to and approved the final manuscript. EB is responsible for the overall content as the guarantor.
The study was funded by the National Institute for Health Research Health Protection Re-search Unit (NIHR HPRU) in Emergency Preparedness and Response, a partnership between Public Health England, King’s College London and the University of East Anglia (grant number 200890). DW and RA’s time on the project was also supported by the NIHR HPRU in Behavioural Science and Evaluation, a partnership between Public Health England and the University of Bristol.
None declared.
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Data are available in a public, open access repository. The dataset is publicly available from Open Science Framework:
Not applicable.
The study was reviewed and approved by Public Health England’s Research and Ethics Governance Group (RD432). Participants gave informed consent to participate in the study before taking part.