Epidemiol Mikrobiol Imunol . 2021 Spring;70(1):3-9.

    • PMID: 33853332

    Abstract

    Objective: To point out possible infection with SARS-CoV-2 in symptomatic patients despite repeated negative nasopharyngeal swab tests for SARS-CoV-2.

    Material and methods: A retrospective observational study carried out at the Na Bulovce Hospital from the beginning of the pandemic until November 2020 included patients (1) who had symptoms compatible with COVID-19; (2) whose nasopharyngeal swab PCR tests in the presence of acute respiratory infection symptoms yielded two consecutive negative results; (3) in whom SARS-CoV-2 infection was subsequently confirmed by serology. Basic demographic and epidemiological data, symptoms, laboratory test results, X-ray findings and timing of virological tests were analysed for these patients.

    Results: Seventeen patients met the inclusion criteria, 14 men and three women, aged 19-84 years with a median of 59 years, of whom 14 were hospitalized and three were treated as outpatients. Only seven patients were aware of the previous contact with an infected person. The main symptoms were fever, cough, headache, weakness, fatigue and shortness of breath. Pneumonia was found in 12 patients, four of whom developed respiratory insufficiency requiring ventilatory support. Most patients showed a uniform combination of haematological, biochemical and radio-logical findings: absence of eosinophils and increased polymorphonuclear/lymphocyte ratio; elevation of serum lactate dehydrogenase; elevation of CRP without rise of procalcitonin; typical chest CT or X-ray findings. All patients recovered. Coronavirus antigen test was performed in six patients, with all of them testing negative. SARS-CoV-2 infection was confirmed serologically by the detection of specific IgG and IgA in all 17 patients and also IgM in six patients, not before day 8 of the onset of symptoms.

    Conclusions: Our study showed that some patients with acute COVID-19 may test repeatedly negative by nasopharyngeal swab PCR. These cases should be interpreted as a low viral load in the upper respiratory tract rather than false negativity of PCR. Such alternative is not envisaged in the algorithms used. Considering our results, the following recommendation can be made: If, despite negative PCR tests, COVID-19 is still suspected based on clinical symptoms and epidemiological evidence, preliminary diagnosis can be made on the basis of comprehensive assessment of the laboratory test and X-ray findings. Final confirmation of the aetiology relies on serological tests performed two weeks after the onset of symptoms.

    Keywords: COVID-19; PCR tests; Serology; diagnosis; diagnostics.

    Publication types

    • Observational Study

    MeSH terms

    • Adult
    • Aged
    • Aged, 80 and over
    • COVID-19*
    • Coronavirus Infections* / epidemiology
    • Female
    • Humans
    • Male
    • Middle Aged
    • Pandemics
    • Polymerase Chain Reaction
    • SARS-CoV-2
    • Young Adult
    Can you have a negative PCR test and still have COVID?
    Conclusions: Our study showed that some patients with acute COVID-19 may test repeatedly negative by nasopharyngeal swab PCR. These cases should be interpreted as a low viral load in the upper respiratory tract rather than false negativity of PCR. more
    Can you be contagious with Covid and test negative?
    If you had a negative test when symptoms started, it's still best to isolate at home for two to three more days, to monitor your symptoms and prevent spreading infection. (That's because there is a chance of false negatives with antigen tests, which means you can still have COVID with a negative test.) more
    How soon after you test positive for COVID can you test negative?
    At least 5 days. If you are: Asymptomatic: Isolate for 5 days after the first positive test. more
    Does a negative COVID test mean not contagious?
    If you get multiple negative test results, it is more likely that you are not infected with COVID. If you are feeling sick, even if it is not COVID, it's still a good idea to stay home and not infect others. more
    Can you have symptoms of Covid but test negative?
    If you have some symptoms and then feel healthy again, and have multiple negative tests throughout that time, it's possible that your immune system was able to prevent the virus levels from getting high enough to be detected on an antigen or even a PCR test. more
    Can you have COVID but test negative twice?
    If you have some symptoms and then feel healthy again, and have multiple negative tests throughout that time, it's possible that your immune system was able to prevent the virus levels from getting high enough to be detected on an antigen or even a PCR test. Thanks, immune system! more
    Why do I have COVID symptoms but test negative?
    If you have some symptoms and then feel healthy again, and have multiple negative tests throughout that time, it's possible that your immune system was able to prevent the virus levels from getting high enough to be detected on an antigen or even a PCR test. more
    Are you contagious if your COVID test is negative?
    If you get multiple negative test results, it is more likely that you are not infected with COVID. If you are feeling sick, even if it is not COVID, it's still a good idea to stay home and not infect others. more
    Can I test positive for Covid then negative?
    Some people with mild infections may test negative on an antigen test, but positive on a PCR test. This would mean that they have COVID, but don't have enough virus to turn an antigen test positive. more
    Is C negative on a Covid test?
    If you have 1 line by C, and 1 line by T this is called a positive result. The lines can be bright or faint. You have COVID-19. If you have 1 line by C, and no line by T this is called a negative result. more
    How long does it take to test negative after a positive COVID test?
    At least 5 days. If you are: Asymptomatic: Isolate for 5 days after the first positive test. more

    Source: pubmed.ncbi.nlm.nih.gov

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