COVID-19 laboratory findings: Difference between revisions
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* [[Leukocytosis]] | * [[Leukocytosis]] | ||
**[[Leukocytosis]] is seen in 11.4% of patients with severe [[COVID-19]] infection compared to 4.8% of patients with non-severe infection.<ref name="pmid32109013" /> | |||
**In patients with COVID-19 infection, leukocytosis may be an indication of a bacterial infection or superinfection.<ref name="pmid32191623">{{cite journal| author=Lippi G, Plebani M| title=The critical role of laboratory medicine during coronavirus disease 2019 (COVID-19) and other viral outbreaks. | journal=Clin Chem Lab Med | year= 2020 | volume= 58 | issue= 7 | pages= 1063-1069 | pmid=32191623 | doi=10.1515/cclm-2020-0240 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=32191623 }} </ref> | |||
* [[COVID-19-associated neutrophilia|Neutrophilia]] | * [[COVID-19-associated neutrophilia|Neutrophilia]] | ||
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* Increase in monocyte distribution width (MDW) | * 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.<ref name="pmid32191623" /> | |||
* [[Thrombocytosis]] | * [[Thrombocytosis]] | ||
**[[Thrombocytosis]] has been reported in 4% of patients with [[COVID-19]] infection.<ref name="pmid32007143">{{cite journal| author=Chen N, Zhou M, Dong X, Qu J, Gong F, Han Y | display-authors=etal| title=Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study. | journal=Lancet | year= 2020 | volume= 395 | issue= 10223 | pages= 507-513 | pmid=32007143 | doi=10.1016/S0140-6736(20)30211-7 | pmc=7135076 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=32007143 }} </ref> | |||
* [[COVID-19-associated thrombocytopenia|Thrombocytopenia]] | * [[COVID-19-associated thrombocytopenia|Thrombocytopenia]] | ||
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* Increased [[procalcitonin]] | * Increased [[procalcitonin]] | ||
**Increase in [[procalcitonin]] is seen in 13.7% of patients with severe [[COVID-19]] infection compared to 3.7% of patients with non-severe infection.<ref name="pmid32109013" /> | **Increase in [[procalcitonin]] is seen in 13.7% of patients with severe [[COVID-19]] infection compared to 3.7% of patients with non-severe infection.<ref name="pmid32109013" /> | ||
**In sepsis, the activation and adherence of [[Monocyte|monocytes]] increase [[procalcitonin]], therefore [[procalcitonin]] in a biomarker for sepsis and septic shock.<ref name="pmid24982830">{{cite journal| author=Meisner M| title=Update on procalcitonin measurements. | journal=Ann Lab Med | year= 2014 | volume= 34 | issue= 4 | pages= 263-73 | pmid=24982830 | doi=10.3343/alm.2014.34.4.263 | pmc=4071182 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24982830 }} </ref> | **In sepsis, the activation and adherence of [[Monocyte|monocytes]] increase [[procalcitonin]], therefore [[procalcitonin]] in a biomarker for sepsis and septic shock.<ref name="pmid24982830">{{cite journal| author=Meisner M| title=Update on procalcitonin measurements. | journal=Ann Lab Med | year= 2014 | volume= 34 | issue= 4 | pages= 263-73 | pmid=24982830 | doi=10.3343/alm.2014.34.4.263 | pmc=4071182 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24982830 }} </ref> | ||
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* Increased [[ferritin]] | * Increased [[ferritin]] | ||
**There have been different reports regarding the association of increase in [[ferritin]] with death in COVID-19 infection; for example, there has been a report that increase in [[ferritin]] is associated with [[Acute respiratory distress syndrome|acute respiratory distress syndrome (ARDS)]] but not death<ref name="pmid32167524">{{cite journal| author=Wu C, Chen X, Cai Y, Xia J, Zhou X, Xu S | display-authors=etal| title=Risk Factors Associated With Acute Respiratory Distress Syndrome and Death in Patients With Coronavirus Disease 2019 Pneumonia in Wuhan, China. | journal=JAMA Intern Med | year= 2020 | volume= | issue= | pages= | pmid=32167524 | doi=10.1001/jamainternmed.2020.0994 | pmc=7070509 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=32167524 }} </ref>, while another one reports an association between increase in [[ferritin]] and death in COVID-19 infection<ref name="pmid32171076">{{cite journal| author=Zhou F, Yu T, Du R, Fan G, Liu Y, Liu Z | display-authors=etal| title=Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. | journal=Lancet | year= 2020 | volume= 395 | issue= 10229 | pages= 1054-1062 | pmid=32171076 | doi=10.1016/S0140-6736(20)30566-3 | pmc=7270627 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=32171076 }} </ref | **There have been different reports regarding the association of increase in [[ferritin]] with death in COVID-19 infection; for example, there has been a report that increase in [[ferritin]] is associated with [[Acute respiratory distress syndrome|acute respiratory distress syndrome (ARDS)]] but not death<ref name="pmid32167524">{{cite journal| author=Wu C, Chen X, Cai Y, Xia J, Zhou X, Xu S | display-authors=etal| title=Risk Factors Associated With Acute Respiratory Distress Syndrome and Death in Patients With Coronavirus Disease 2019 Pneumonia in Wuhan, China. | journal=JAMA Intern Med | year= 2020 | volume= | issue= | pages= | pmid=32167524 | doi=10.1001/jamainternmed.2020.0994 | pmc=7070509 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=32167524 }} </ref>, while another one reports an association between increase in [[ferritin]] and death in COVID-19 infection<ref name="pmid32171076">{{cite journal| author=Zhou F, Yu T, Du R, Fan G, Liu Y, Liu Z | display-authors=etal| title=Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. | journal=Lancet | year= 2020 | volume= 395 | issue= 10229 | pages= 1054-1062 | pmid=32171076 | doi=10.1016/S0140-6736(20)30566-3 | pmc=7270627 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=32171076 }} </ref | ||
* Decreased [[albumin]] | * Decreased [[albumin]] | ||
** As a negative acute‐phase reactant, circulatory level of albumin may fall as a result of increased transcapillary leakage or reduced hepatic synthesis mediated by inflammatory cytokines such as [[IL-6|interleukin‐6]] and [[tumor necrosis factor alpha]].<ref name="ChiGibson2019">{{cite journal|last1=Chi|first1=Gerald|last2=Gibson|first2=C. Michael|last3=Liu|first3=Yuyin|last4=Hernandez|first4=Adrian F.|last5=Hull|first5=Russell D.|last6=Cohen|first6=Alexander T.|last7=Harrington|first7=Robert A.|last8=Goldhaber|first8=Samuel Z.|title=Inverse relationship of serum albumin to the risk of venous thromboembolism among acutely ill hospitalized patients: Analysis from the APEX trial|journal=American Journal of Hematology|volume=94|issue=1|year=2019|pages=21–28|issn=03618609|doi=10.1002/ajh.25296}}</ref> Consequently, [[hypoalbuminemia]] may indicate a hyperinflammatory status associated with [[COVID-19]]. | ** As a negative acute‐phase reactant, circulatory level of albumin may fall as a result of increased transcapillary leakage or reduced hepatic synthesis mediated by inflammatory cytokines such as [[IL-6|interleukin‐6]] and [[tumor necrosis factor alpha]].<ref name="ChiGibson2019">{{cite journal|last1=Chi|first1=Gerald|last2=Gibson|first2=C. Michael|last3=Liu|first3=Yuyin|last4=Hernandez|first4=Adrian F.|last5=Hull|first5=Russell D.|last6=Cohen|first6=Alexander T.|last7=Harrington|first7=Robert A.|last8=Goldhaber|first8=Samuel Z.|title=Inverse relationship of serum albumin to the risk of venous thromboembolism among acutely ill hospitalized patients: Analysis from the APEX trial|journal=American Journal of Hematology|volume=94|issue=1|year=2019|pages=21–28|issn=03618609|doi=10.1002/ajh.25296}}</ref> Consequently, [[hypoalbuminemia]] may indicate a hyperinflammatory status associated with [[COVID-19]]. | ||
**[[Albumin]] may be decreased in many conditions such as [[sepsis]], renal disease or [[malnutrition]].<ref name="pmid32311826" /> | **[[Albumin]] may be decreased in many conditions such as [[sepsis]], renal disease or [[malnutrition]].<ref name="pmid32311826" /> | ||
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=== Liver Function Tests === | === Liver Function Tests === | ||
The following abnormalities may be observed on [[Liver function tests|LFTs]]: | The following abnormalities may be observed on [[Liver function tests|LFTs]]: | ||
* Increased [[Aspartate aminotransferase|aspartate aminotrasnferase]] ([[Aspartate transaminase|AST]]): | * Increased [[Aspartate aminotransferase|aspartate aminotrasnferase]] ([[Aspartate transaminase|AST]]): | ||
**Increase in [[Aspartate transaminase|AST]] is seen in 39.4% of patients with severe [[COVID-19]] infection compared to 18.2% of patients with non-severe infection. | **Increase in [[Aspartate transaminase|AST]] is seen in 39.4% of patients with severe [[COVID-19]] infection compared to 18.2% of patients with non-severe infection.<ref name="pmid32109013" /> | ||
*In patients with [[COVID-19]] infection, increase in [[aminotransferases]] may indicate injury to the [[liver]] or multi-system damage.<ref name="pmid32191623" /> | |||
* Increased [[alanine aminotransferase]] ([[Alanine transaminase|ALT]]): | * Increased [[alanine aminotransferase]] ([[Alanine transaminase|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. | **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.<ref name="pmid32109013" /> | ||
** [[Alanine transaminase|ALT]] is produced by liver cells and is increased in liver conditions. | **[[Alanine transaminase|ALT]] is produced by liver cells and is increased in liver conditions.<ref name="pmid32311826" /> | ||
**In patients with [[COVID-19]] infection, increase in [[aminotransferases]] may indicate injury to the liver or multi-system damage. | **In patients with [[COVID-19]] infection, increase in [[aminotransferases]] may indicate injury to the liver or multi-system damage.<ref name="pmid32191623" /> | ||
*Increase in total [[bilirubin]] | *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. | **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.<ref name="pmid32109013" /> | ||
**Bilirubin is produced by liver cells and increases in liver and biliary conditions. | **Bilirubin is produced by liver cells and increases in liver and biliary conditions.<ref name="pmid32311826" /> | ||
**In patients with COVID-19 infection, increase in total bilirubin may indicate injury to the liver. | **In patients with COVID-19 infection, increase in total bilirubin may indicate injury to the liver.<ref name="pmid32191623" /> | ||
=== Renal Function Tests === | === Renal Function Tests === | ||
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* Increased [[Blood urea nitrogen|BUN]] | * Increased [[Blood urea nitrogen|BUN]] | ||
* Increased [[creatinine]] | * Increased [[creatinine]] | ||
**Increase in [[creatinine]] is seen in 4.3% of patients with severe [[COVID-19]] infection compared to 1% of patients with non-severe infection. | **Increase in [[creatinine]] is seen in 4.3% of patients with severe [[COVID-19]] infection compared to 1% of patients with non-severe infection.<ref name="pmid32109013" /> | ||
**Creatinin is produced in the liver and excreted by the kidneys; [[creatinine]] increases when there is decrease in [[glomerular filtration rate]]. | **Creatinin is produced in the liver and excreted by the kidneys; [[creatinine]] increases when there is decrease in [[glomerular filtration rate]].<ref name="pmid32311826" /> | ||
**In patients with COVID-19 infection, increase in [[creatinine]] may indicate injury to the kidneys. | **In patients with COVID-19 infection, increase in [[creatinine]] may indicate injury to the kidneys.<ref name="pmid32191623" /> | ||
=== Markers of Cell Damage === | === Markers of Cell Damage === | ||
The following markers of [[cellular]] damage may be altered: | The following markers of [[cellular]] damage may be altered: | ||
* Increased [[troponin]] | * Increased [[troponin]] | ||
**In myocardial infarction and [[Acute coronary syndromes|acute coronary syndrome]] are used for diagnosis. | **In myocardial infarction and [[Acute coronary syndromes|acute coronary syndrome]] are used for diagnosis.<ref name="pmid32311826" /> | ||
**In patients with COVID-19 infection, increase in cardiac troponins may indicate cardiac injury. | **In patients with COVID-19 infection, increase in cardiac troponins may indicate cardiac injury.<ref name="pmid32191623" /> | ||
* Increased [[myoglobin]] | * Increased [[myoglobin]] | ||
* Increased [[lactate dehydrogenase]] ([[Lactate dehydrogenase|LDH]]) | * Increased [[lactate dehydrogenase]] ([[Lactate dehydrogenase|LDH]]) | ||
** Increase in [[Lactate dehydrogenase|LDH]] is seen in 58.1% of patients with severe [[COVID-19]] infection compared to 37.2% of patients with non-severe infection. | **Increase in [[Lactate dehydrogenase|LDH]] is seen in 58.1% of patients with severe [[COVID-19]] infection compared to 37.2% of patients with non-severe infection.<ref name="pmid32109013" /> | ||
** LDH is expressed in almost all cells and an increase in [[LDH]] could be seen in damage to any of the cell types. | **LDH is expressed in almost all cells and an increase in [[LDH]] could be seen in damage to any of the cell types.<ref name="pmid32311826" /> | ||
**In patients with COVID-19 infection, increase in [[Lactate dehydrogenase|LDH]] may indicate injury to the lungs or multi-system damage. | **In patients with COVID-19 infection, increase in [[Lactate dehydrogenase|LDH]] may indicate injury to the lungs or multi-system damage.<ref name="pmid32191623" /> | ||
* Decreased [[albumin]] | * Decreased [[albumin]] | ||
**[[Albumin]] may be decreased in many conditions such as [[sepsis]], renal disease or [[malnutrition]].<ref name="pmid32311826" /> | |||
**In patients with COVID-19 infection, decrease in [[albumin]] may indicate liver function abnormality.<ref name="pmid32191623" /> | |||
* Increased [[Creatine kinase|creatine kinase]] | * Increased [[Creatine kinase|creatine kinase]] | ||
==References== | ==References== | ||
{{reflist|2}} | {{reflist|2}} | ||
Revision as of 20:48, 11 July 2020
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COVID-19 laboratory findings On the Web |
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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]
Overview
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
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.
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.
| 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.[1]
- In patients with COVID-19 infection, leukocytosis may be an indication of a bacterial infection or superinfection.[2]
- 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.[2]
- Thrombocytosis
- Thrombocytosis has been reported in 4% of patients with COVID-19 infection.[3]
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.[1]
- CRP is an acute phase reactant that increases in conditions with inflammation.[4]
- In patients with COVID-19 infection, increase in CRP may be an indication of severe viral infection or sepsis and viremia.[2]
- Increased IL-6
- Increased procalcitonin
- Increase in procalcitonin is seen in 13.7% of patients with severe COVID-19 infection compared to 3.7% of patients with non-severe infection.[1]
- In sepsis, the activation and adherence of monocytes increase procalcitonin, therefore procalcitonin in a biomarker for sepsis and septic shock.[6]
- In patients with COVID-19 infection, increase in procalcitonin may be an indication of bacterial infection or superinfection.[2]
- Increased ferritin
- There have been different reports regarding the association of increase in ferritin with death in COVID-19 infection; for example, there has been a report that increase in ferritin is associated with acute respiratory distress syndrome (ARDS) but not death[5], while another one reports an association between increase in ferritin and death in COVID-19 infection Consequently, hypoalbuminemia may indicate a hyperinflammatory status associated with COVID-19.
- Albumin may be decreased in many conditions such as sepsis, renal disease or malnutrition.[4]
- In patients with COVID-19 infection, decrease in albumin may indicate liver function abnormality.[2]
Liver Function Tests
The following abnormalities may be observed on LFTs:
- Increased aspartate aminotrasnferase (AST):
- In patients with COVID-19 infection, increase in aminotransferases may indicate injury to the liver or multi-system damage.[2]
- 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.[1]
- ALT is produced by liver cells and is increased in liver conditions.[4]
- In patients with COVID-19 infection, increase in aminotransferases may indicate injury to the liver or multi-system damage.[2]
- 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.[1]
- Bilirubin is produced by liver cells and increases in liver and biliary conditions.[4]
- In patients with COVID-19 infection, increase in total bilirubin may indicate injury to the liver.[2]
Renal Function Tests
Renal function tests may show the following:
- Increased BUN
- Increased creatinine
- Increase in creatinine is seen in 4.3% of patients with severe COVID-19 infection compared to 1% of patients with non-severe infection.[1]
- Creatinin is produced in the liver and excreted by the kidneys; creatinine increases when there is decrease in glomerular filtration rate.[4]
- In patients with COVID-19 infection, increase in creatinine may indicate injury to the kidneys.[2]
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.[4]
- In patients with COVID-19 infection, increase in cardiac troponins may indicate cardiac injury.[2]
- 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.[1]
- LDH is expressed in almost all cells and an increase in LDH could be seen in damage to any of the cell types.[4]
- In patients with COVID-19 infection, increase in LDH may indicate injury to the lungs or multi-system damage.[2]
- Decreased albumin
- Increased creatine kinase
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 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). - ↑ 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). - ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Frater JL, Zini G, d'Onofrio G, Rogers HJ (2020). "COVID-19 and the clinical hematology laboratory". Int J Lab Hematol. 42 Suppl 1: 11–18. doi:10.1111/ijlh.13229. PMC 7264622 Check
|pmc=value (help). PMID 32311826 Check|pmid=value (help). - ↑ 5.0 5.1 Wu C, Chen X, Cai Y, Xia J, Zhou X, Xu S; et al. (2020). "Risk Factors Associated With Acute Respiratory Distress Syndrome and Death in Patients With Coronavirus Disease 2019 Pneumonia in Wuhan, China". JAMA Intern Med. doi:10.1001/jamainternmed.2020.0994. PMC 7070509 Check
|pmc=value (help). PMID 32167524 Check|pmid=value (help). - ↑ 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.