An interesting correspondence by Lekpa and others published in The Lancet Infectious Diseases May 28th 2021 suggests that this is indeed the case.  

They feel that the clinical case and context for the suspicion of COVID-19 needs to be brought into the equation. 

They suggest that it is not unusual to see a patient with a suggestive clinical presentation with or without chest CT imaging suggestive of COVID-19 but a negative lateral flow rapid test or negative PCR test.  

They describe these false negative results as being explained by a number of factors such as:

  • Viral load, which is associated with disease course and disease severity
  • Sputum or throat swab sample quality, this must contain sufficient cellular material for detection
  • Kit performance, sample transportation and sample storage conditions
  • Lack of standardised operating procedures.
  • Interpretation of results; and quality control issues. 

Interestingly, they describe that patients with a high platelet count or C-reactive protein levels are at an increased risk of having a false negative first PCR swab test.  

They go on to suggest that in the presence of a negative screening result for SARS-CoV-2, we as clinicians should not ignore potential differential diagnoses which need to be ruled out. 

They suggest that in the case of a strong clinical suspicion but negative antigen rapid diagnostic tests lateral flow or negative PCR results that the patient should be resampled by a different operator from the one who did the first test. 

Furthermore, they considered adding antibody based tests to the proposed armamentarium of diagnostic tools to COVID-19 in those who are symptomatic and suggest that this could improve the positive predictive value of the whole strategy.  

If there is a high clinical suspicion, then they consider that it is wise to perform up to three tests to rule out the diagnosis. 

Furthermore, if the clinical suspicion remains strong, then they suggest that chest CT imaging should be performed as this has a reasonably good sensitivity and severity grading role.  

The London General Practice, the leading London doctors’ clinic is proud to be on the approved Government website for all COVID testing.  This includes fit to fly, rapid antigen testing, PCR COVID testing, and all necessary travel PCR tests.  As such, this would include the day two test, day two and eight test and the day five test for release test.

Dr Paul Ettlinger
BM, DRCOG, FRCGP, FRIPH, DOccMed

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