COVID-19 laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Syed Hassan A. Kazmi BSc, MD [2] Shakiba Hassanzadeh, MD[3]


Laboratory tests can be done to confirm whether illness may be caused by human coronaviruses. Specific laboratory tests include serology for viral antigen, molecular testing and viral culture. All these tests can be used to confirm infection with coronavirus. Non-specific laboratory findings in COVID-19 include lymphocytopenia, thrombocytopenia, elevated C-Reactive protein, elevated liver function tests (ALT, AST), increased creatine kinase, increased D-Dimer and an increase in the levels of markers of cell damage e.g. troponin, lactate dehydrogenase, interleukin-4, procalcitonin.

Tests to be Performed for Patients Meeting COVID-19 Case Definition

Antigen tests

Abbott BinaxNOW Ag Card detects the SARS-CoV-2 nucleocapsid protein antigen but does not differentiate between SARS-CoV and SARS-CoV2.[1]

Molecular tests

Molecular tests are used to diagnose active infection (presence of COVID-19) in people who are thought to be infected with COVID-19 based on their clinical symptoms and having links to places where COVID-19 has been reported.

Real-time reverse-transcription polymerase chain reaction (rRT-PCR) assays are molecular tests that can be used to detect viral RNA in clinical samples.

Nucleic acid amplification test

  • The importance of the need for confirmation of results of testing with pan-coronavirus primers is underscored by the fact that four human coronaviruses (HcoVs) are endemic globally: HCoV-229E, HCoV-NL63, HCoV-HKU1 as well as HCoV-OC43. The latter two are betacoronaviruses. Two other betacoronaviruses that cause zoonotic infection in humans are MERS-CoV, acquired by contact with dromedary camels and SARS arising from civets and cave-dwelling horseshoe bats.
  • The accuracy of nucleic acid amplification tests have been systematically reviewed[2].
  • PCR has been used to test salivary specimens[3][4].

Serological testing

  • Serological testing may be useful to confirm immunologic response to a pathogen from a specific viral group, e.g. coronavirus.
  • Best results from serologic testing requires the collection of paired serum samples (in the acute and convalescent phase) from cases under investigation.
  • The accuracy of serologic tests have been systematically reviewed[5][6].
Tests to be performed for patients meeting case definition
Laboratory Test Source of Specimen Additional Comments
In laboratories that have validated broad coronavirus RT-PCR

assays it is advised to check the primers against the published

2019-nCoV sequence and check if primers are overlapping and

have the capacity to detect the 2019-nCoV. On a positive results

sequencing should be performed to determine the precise virus

detected (e.g. on an amplicon of a non-conserved region).

Respiratory secretions Collect on presentation. Done by an expert laboratory.
NAAT for 2019n-CoV when it becomes available (assays currently under validation) Respiratory secretions Collect on presentation. Done by an expert laboratory until validation has been finalized.
Serology, broad corona virus serology on paired samples if available. Respiratory secretions Paired samples necessary for confirmation, the first sample collected in week 1 of illness, and the second collected 3-4 weeks later. If a single serum sample can be collected, collect at least 3 weeks after onset of symptoms. Done by the expert laboratory until more information on the performance of available assays.

Laboratory Findings

Complete Blood Count

Complete blood count may show the following:

  • Leukocytosis
    • Leukocytosis is seen in 11.4% of patients with severe COVID-19 infection compared to 4.8% of patients with non-severe infection.[7]
    • In patients with COVID-19 infection, leukocytosis may be an indication of a bacterial infection or superinfection.[8]
  • Increase in monocyte distribution width (MDW)
    • MDW was found to be increased in all patients with COVID-19 infection, particularly in those with the worst conditions.[8]

Acute Phase Reactants

The following inflammatory markers may be altered:

  • Increased C-reactive protein
    • Increase in CRP is seen in 81.5% of patients with severe COVID-19 infection compared to 56.4% of patients with non-severe infection.[7]
    • CRP is an acute phase reactant that increases in conditions with inflammation.[10]
    • In patients with COVID-19 infection, increase in CRP may be an indication of severe viral infection or sepsis and viremia.[8]

Liver Function Tests

The following abnormalities may be observed on LFTs:

  • Increased aspartate aminotrasnferase (AST):
    • Increase in AST is seen in 39.4% of patients with severe COVID-19 infection compared to 18.2% of patients with non-severe infection.[7]
    • In patients with COVID-19 infection, increase in aminotransferases may indicate injury to the liver or multi-system damage.[8]
  • Increased alanine aminotransferase (ALT):
    • Increase in ALT is seen in 28.1% of patients with severe COVID-19 infection compared to 19.8% of patients with non-severe infection.[7]
    • ALT is produced by liver cells and is increased in liver conditions.[10]
    • In patients with COVID-19 infection, increase in aminotransferases may indicate injury to the liver or multi-system damage.[8]
  • Increase in total bilirubin
    • Increase in total bilirubin is seen in 13.3% of patients with severe COVID-19 infection compared to 9.9% of patients with non-severe infection.[7]
    • Bilirubin  is produced by liver cells and increases in liver and biliary conditions.[10]
    • In patients with COVID-19 infection, increase in total bilirubin may indicate injury to the liver.[8]

Renal Function Tests

Renal function tests may show the following:

Markers of Cell Damage

The following markers of cellular damage may be altered:

  • Increased troponin
    • In myocardial infarction and acute coronary syndrome are used for diagnosis.[10]
    • In patients with COVID-19 infection, increase in cardiac troponins may indicate cardiac injury.[8]
  • Increased myoglobin
  • Increased lactate dehydrogenase (LDH)
    • Increase in LDH is seen in 58.1% of patients with severe COVID-19 infection compared to 37.2% of patients with non-severe infection.[7]
    • LDH is expressed in almost all cells and an increase in LDH could be seen in damage to any of the cell types.[10]
    • In patients with COVID-19 infection, increase in LDH may indicate injury to the lungs or multi-system damage.[8]
  • Increased creatine kinase


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  3. Wyllie AL, Fournier J, Casanovas-Massana A, Campbell M, Tokuyama M, Vijayakumar P; et al. (2020). "Saliva or Nasopharyngeal Swab Specimens for Detection of SARS-CoV-2". N Engl J Med. doi:10.1056/NEJMc2016359. PMID 32857487 Check |pmid= value (help).
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  5. Deeks JJ, Dinnes J, Takwoingi Y, Davenport C, Spijker R, Taylor-Phillips S; et al. (2020). "Antibody tests for identification of current and past infection with SARS-CoV-2". Cochrane Database Syst Rev. 6: CD013652. doi:10.1002/14651858.CD013652. PMID 32584464 Check |pmid= value (help).
  6. Lisboa Bastos M, Tavaziva G, Abidi SK, Campbell JR, Haraoui LP, Johnston JC; et al. (2020). "Diagnostic accuracy of serological tests for covid-19: systematic review and meta-analysis". BMJ. 370: m2516. doi:10.1136/bmj.m2516. PMC 7327913 Check |pmc= value (help). PMID 32611558 Check |pmid= value (help).
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 Guan WJ, Ni ZY, Hu Y, Liang WH, Ou CQ, He JX; et al. (2020). "Clinical Characteristics of Coronavirus Disease 2019 in China". N Engl J Med. 382 (18): 1708–1720. doi:10.1056/NEJMoa2002032. PMC 7092819 Check |pmc= value (help). PMID 32109013 Check |pmid= value (help).
  8. 8.00 8.01 8.02 8.03 8.04 8.05 8.06 8.07 8.08 8.09 8.10 Lippi G, Plebani M (2020). "The critical role of laboratory medicine during coronavirus disease 2019 (COVID-19) and other viral outbreaks". Clin Chem Lab Med. 58 (7): 1063–1069. doi:10.1515/cclm-2020-0240. PMID 32191623 Check |pmid= value (help).
  9. Chen N, Zhou M, Dong X, Qu J, Gong F, Han Y; et al. (2020). "Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study". Lancet. 395 (10223): 507–513. doi:10.1016/S0140-6736(20)30211-7. PMC 7135076 Check |pmc= value (help). PMID 32007143 Check |pmid= value (help).
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  12. Meisner M (2014). "Update on procalcitonin measurements". Ann Lab Med. 34 (4): 263–73. doi:10.3343/alm.2014.34.4.263. PMC 4071182. PMID 24982830.
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  14. Chi, Gerald; Gibson, C. Michael; Liu, Yuyin; Hernandez, Adrian F.; Hull, Russell D.; Cohen, Alexander T.; Harrington, Robert A.; Goldhaber, Samuel Z. (2019). "Inverse relationship of serum albumin to the risk of venous thromboembolism among acutely ill hospitalized patients: Analysis from the APEX trial". American Journal of Hematology. 94 (1): 21–28. doi:10.1002/ajh.25296. ISSN 0361-8609.