Covid-19 tests: The safety implications of false negatives

  • 22nd May 2020

The number of people accessing Covid-19 testing in the UK continues to increase. Health Secretary, Matt Hancock recently announced, that anyone over the age of five years old who is showing symptoms is eligible for a test.[1] However, there are concerns that the rate of ‘false negative’ test results could be as high as 30% and a significant number of people are wrongly being told they do not have the virus.[2] This could be due to the particularly difficult nature of obtaining the swab, which requires someone to take a sample from the very back of the mouth or deep from inside the nose.

“Swabbing patients using the correct technique is paramount in ensuring an accurate result. Nasal swabs need to be taken from far back in the nasal pharynx and is often uncomfortable for the patient. By simply swabbing the inside of the nasal passage is not deep enough to verify that the virus is present. I am unsure that all clinical staff have been taught the correct way to swab patients.” Claire Cox, Intensive Care Outreach Nurse.

Members of the public are now able to request self-testing kits to do at home if they are experiencing symptoms. If clinicians like Claire are finding the test challenging to perform on others, it is likely that patients could struggle to swab deep enough into their own nasal pharynx (7-8cm). There is a risk that as the number of people testing themselves increases, so too will the rate of false negative results.

Testing is a key element of the UK’s Covid-19 infection control strategy.[3] A high, and potentially rising, rate of false negative results means that a significant number of people could be carrying the virus, wrongly reassured they are not infectious. In this blog, we look at some of the associated safety risks.

Safe zones compromised

Covid-19 testing is being used to inform decisions around infection control. If there are people moving into or between health and social care settings (patients or staff), who have tested negatively and are not showing typical symptoms of Covid-19, they will likely be treated accordingly. For example, they may be placed in ‘green’ areas, dedicated for those who do not have the virus. These areas are designed to protect non Covid-19 patients but there is a risk that some patients could have had a false negative test result and slipped through the net, compromising safety measures.

A danger of misdiagnosis

If clinicians are relying on test results being accurate, people who are experiencing symptoms but are told they are Covid-19 negative may be dismissed or misdiagnosed. In a recent blog published on the hub, patient ‘Sarah’ explains how she was discharged from A&E, following a negative test result, and diagnosed with anxiety. A few days on she deteriorated, needing to be admitted to hospital again, this time by ambulance. She was told by paramedics that, according to her observations, she should have been in a coma. Doctors later confirmed that her initial test result had been falsely negative and that she did have Covid-19. Sarah also expressed concern for the paramedics who were not wearing adequate protection to treat someone with Covid-19, because they were wrongly reassured by the test that she was negative.[4]

Impact in the community

If members of the public test falsely negatively for Covid-19, there is the risk that they will not isolate and will spread the infection further as they access supermarkets, pharmacies and don’t distance from members of their household. There may also be cases where patients who had a false negative were incorrectly advised they were safe to return to work. For key workers in particular, this would increase the risk of spreading the virus to their colleagues and service users.

Impact on mental health and recovery

There is a risk that a patient’s mental health and wellbeing could deteriorate if they receive a negative test result but are in fact suffering from Covid-19. This is of particular concern in relation to the significant number who are experiencing a slow and debilitating recovery but have not necessarily needed hospital care.[5][6] We are hearing from Covid-19 support groups that these ‘moderate’ sufferers are often left feeling lonely, depressed and frustrated that they are unable to get back on their feet as quickly as they feel they should.[7] There seems to be little support for this group, particularly where they have tested negatively and their symptoms do not align with the official list of symptoms for coronavirus infection.

Some people who were sure they had the virus but received a negative test result, have ended up doubting themselves. They pushed their bodies too hard too soon, causing relapses in symptoms and they have subsequently faced further mental health challenges. In an anonymous account on the hub, one patient explains how a false negative caused her mental health to deteriorate.

“I thought that I should be physically active if I didn't have Covid-19, so I pushed myself and berated myself when I repeatedly became unable to breath with a pounding heart upon any exertion. I couldn't cope caring for my four children and was in a 'critical' dangerous mental state many times. I self-harmed to try and cut off from feeling so awful.”[8]

Concluding thoughts

Patient Safety Learning are concerned that false negative test results could present several risks to patient safety and we ask the following questions:

  • How are the number of false negative tests being monitored and is this data being publicly reported?
  • Is adequate research being undertaken to understand the cause/s behind the false negative results?
  • What steps are being taken to reduce the testing problems commonly encountered by healthcare professionals that lead to false negatives?
  • Do staff taking swabs feel adequately trained and supported?
  • Is patient feedback around the ease of the self-testing process being captured and reported on?
  • Is the current support and guidance for people who are home-testing fit-for-purpose and endorsed by human factors experts?
  • What is the guidance for caring for patients in hospitals and care settings when they are experiencing symptoms of Covid-19 but have tested negatively?
  • What support is available for patients who believe they have had Covid-19 and are experiencing debilitating symptoms weeks later, but may not have been tested or may have tested negatively?
  • A highly accurate antibody test would help to address some of the concerns raised in this blog and provide a clearer picture of the rate of false negatives. When is that likely to be widely available?

[1] UK Parliament, House of Commons Debate: Covid-19 Response, Volume 676, 18 May 2020.

[2] West, Colin. P, Montori, Victor. M and Sampathkumar, P, Covid-19 Testing: The Threat of False-Negative Results, Science Direct, 11 April 2020.!

[3] Department of Health and Social Care, Coronavirus (COVID-19): scaling up testing programmes, Last Updated 6 April 2020.

[4] Sarah, My ‘false negative’ COVID-19 test put others at risk, Patient Safety Learning’s the hub, 19 May 2020.

[5] The Guardian, ‘Weird as hell’: the Covid-19 patients who have symptoms for months, 15 May 2020.;

[6] Sky News, Prof Tim Spector: There’s no such thing as a ‘classical’ COVID-19 case, Facebook, 18 May 2020.

[7] Facebook, Covid-19 Support Group, Last Accessed 22 May 2020.

[8] Anonymous, ‘False negative’ and the impact on my mental health, Patient Safety Learning’s the hub, 22 May 2020.

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