COVID-19

== Diagnosis ==
{{Further|COVID-19 testing}}

COVID‑19 can provisionally be diagnosed on the basis of symptoms and confirmed using [[reverse transcription polymerase chain reaction]] (RT-PCR) or other [[Nucleic acid test|nucleic acid]] testing of infected secretions.<ref name="pmid32621814">{{#invoke:cite journal || vauthors = Li C, Zhao C, Bao J, Tang B, Wang Y, Gu B | title = Laboratory diagnosis of coronavirus disease-2019 (COVID-19) | journal = Clinica Chimica Acta; International Journal of Clinical Chemistry | volume = 510 | pages = 35–46 | date = November 2020 | pmid = 32621814 | pmc = 7329657 | doi = 10.1016/j.cca.2020.06.045 }}</ref><ref name="jTxKm">{{#invoke:cite journal || vauthors = Ai T, Yang Z, Hou H, Zhan C, Chen C, Lv W, Tao Q, Sun Z, Xia L  | title = Correlation of Chest CT and RT-PCR Testing for Coronavirus Disease 2019 (COVID-19) in China: A Report of 1014 Cases | journal = Radiology | volume = 296 | issue = 2 | pages = E32–E40 | date = August 2020 | pmid = 32101510 | pmc = 7233399 | doi = 10.1148/radiol.2020200642 }}</ref> Along with laboratory testing, chest CT scans may be helpful to diagnose COVID‑19 in individuals with a high clinical suspicion of infection.<ref name="Salehi-2020">{{#invoke:cite journal || vauthors = Salehi S, Abedi A, Balakrishnan S, Gholamrezanezhad A | title = Coronavirus Disease 2019 (COVID-19): A Systematic Review of Imaging Findings in 919 Patients | journal = AJR. American Journal of Roentgenology | volume = 215 | issue = 1 | pages = 87–93 | date = July 2020 | pmid = 32174129 | doi = 10.2214/AJR.20.23034 | doi-access = free | title-link = doi }}</ref> Detection of a past infection is possible with [[Serology|serological tests]], which detect [[Antibody|antibodies]] produced by the body in response to the infection.<ref name="pmid32621814" />

=== Viral testing ===
{{Main|COVID-19 testing}}
[[File:Infektionsschutzzentrum im Rautenstrauch-Joest-Museum, Köln-6313 (cropped).jpg|thumb|Demonstration of a [[nasopharyngeal swab]] for [[COVID‑19 testing]]]]

The standard methods of testing for presence of SARS-CoV-2 are [[nucleic acid test]]s,<ref name="pmid32621814" /><ref name="20200130cdc">{{#invoke:Cite web||date=30 January 2020|title=2019 Novel Coronavirus (2019-nCoV) Situation Summary|url=https://www.cdc.gov/coronavirus/2019-ncov/summary.html|url-status=live|archive-url=https://web.archive.org/web/20200126210549/https://www.cdc.gov/coronavirus/2019-nCoV/summary.html|archive-date=26 January 2020|access-date=30 January 2020|website=U.S. [[Centers for Disease Control and Prevention]] (CDC)}}</ref> which detects the presence of viral RNA fragments.<ref name="WHO_InterimGuidance">{{#invoke:Cite web||title=Coronavirus disease (COVID-19) technical guidance: Laboratory testing for 2019-nCoV in humans |work=[[World Health Organization]] (WHO) |url=https://www.who.int/emergencies/diseases/novel-coronavirus-2019/technical-guidance/laboratory-guidance |access-date=14 March 2020 |archive-url=https://web.archive.org/web/20200315044138/https://www.who.int/emergencies/diseases/novel-coronavirus-2019/technical-guidance/laboratory-guidance |archive-date=15 March 2020 |url-status=live}}</ref> As these tests detect RNA but not infectious virus, its "ability to determine duration of infectivity of patients is limited".<ref name="2k0iS">{{#invoke:cite journal ||vauthors=Bullard J, Dust K, Funk D, Strong JE, Alexander D, Garnett L, Boodman C, Bello A, Hedley A, Schiffman Z, Doan K, Bastien N, Li Y, Van Caeseele PG, Poliquin G |title=Predicting Infectious Severe Acute Respiratory Syndrome Coronavirus 2 From Diagnostic Samples |journal=Clinical Infectious Diseases |volume=71 |issue=10 |pages=2663–2666 |date=December 2020 |pmid=32442256 |pmc=7314198 |doi=10.1093/cid/ciaa638 |doi-access=free |title-link=doi}}</ref> The test is typically done on respiratory samples obtained by a [[nasopharyngeal swab]]; however, a nasal swab or sputum sample may also be used.<ref name="CDC2020Testing">{{#invoke:Cite web||date=11 February 2020|title=Interim Guidelines for Collecting, Handling, and Testing Clinical Specimens from Persons for Coronavirus Disease 2019 (COVID-19) |url=https://www.cdc.gov/coronavirus/2019-ncov/lab/guidelines-clinical-specimens.html|url-status=live|archive-url=https://web.archive.org/web/20200304165907/https://www.cdc.gov/coronavirus/2019-nCoV/lab/guidelines-clinical-specimens.html|archive-date=4 March 2020|access-date=26 March 2020|website=U.S. [[Centers for Disease Control and Prevention]] (CDC)}}</ref><ref name="20200129cdc">{{#invoke:Cite web||date=29 January 2020|title=Real-Time RT-PCR Panel for Detection 2019-nCoV |url=https://www.cdc.gov/coronavirus/2019-ncov/lab/rt-pcr-detection-instructions.html|url-status=live|archive-url=https://web.archive.org/web/20200130202031/https://www.cdc.gov/coronavirus/2019-ncov/lab/rt-pcr-detection-instructions.html|archive-date=30 January 2020|access-date=1 February 2020|website=U.S. [[Centers for Disease Control and Prevention]] (CDC)}}</ref> Results are generally available within hours.<ref name="pmid32621814" /> The WHO has published several testing protocols for the disease.<ref>{{#invoke:Cite web||title=Laboratory testing for 2019 novel coronavirus (2019-nCoV) in suspected human cases|url=https://www.who.int/publications-detail/laboratory-testing-for-2019-novel-coronavirus-in-suspected-human-cases-20200117|url-status=live|archive-url=https://web.archive.org/web/20200317023052/https://www.who.int/publications-detail/laboratory-testing-for-2019-novel-coronavirus-in-suspected-human-cases-20200117|archive-date=17 March 2020|access-date=13 March 2020|website=[[World Health Organization]] (WHO)}}</ref>

Several laboratories and companies have developed serological tests, which detect antibodies produced by the body in response to infection. Several have been evaluated by [[Public Health England]] and approved for use in the UK.<ref name="independent9515466">{{#invoke:cite news||date=14 May 2020|title=NHS staff will be first to get new coronavirus antibody test, medical chief promises|website=The Independent|url=https://www.independent.co.uk/news/uk/home-news/coronavirus-test-antibody-covid-roche-immune-nhs-staff-a9515466.html|access-date=14 May 2020}}</ref>

The [[University of Oxford]]'s CEBM has pointed to mounting evidence<ref name="yFMEP">{{#invoke:Cite web|| vauthors = Heneghan C, Jefferson T |date=1 September 2020|title=Virological characterization of COVID-19 patients that test re-positive for SARS-CoV-2 by RT-PCR|url=https://www.cebm.net/study/virological-characterization-of-covid-19-patients-that-test-re-positive-for-sars-cov-2-by-rt-pcr|access-date=19 September 2020|website=CEBM}}</ref><ref name="2exX5">{{#invoke:cite journal || vauthors = Lu J, Peng J, Xiong Q, Liu Z, Lin H, Tan X, Kang M, Yuan R, Zeng L, Zhou P, Liang C, Yi L, du Plessis L, Song T, Ma W, Sun J, Pybus OG, Ke C  | title = Clinical, immunological and virological characterization of COVID-19 patients that test re-positive for SARS-CoV-2 by RT-PCR | journal = eBioMedicine | volume = 59 | pages = 102960 | date = September 2020 | pmid = 32853988 | pmc = 7444471 | doi = 10.1016/j.ebiom.2020.102960 }}</ref> that "a good proportion of 'new' mild cases and people re-testing positives after quarantine or discharge from hospital are not infectious, but are simply clearing harmless virus particles which their immune system has efficiently dealt with" and have called for "an international effort to standardize and periodically calibrate testing"<ref name="PQGAv">{{#invoke:Cite web|| vauthors = Spencer E, Jefferson T, Brassey J, Heneghan C |date=11 September 2020|title=When is Covid, Covid?|url=https://www.cebm.net/covid-19/when-is-covid-covid/|access-date=19 September 2020|website=The Centre for Evidence-Based Medicine}}</ref> In September 2020, the UK government issued "guidance for procedures to be implemented in laboratories to provide assurance of positive SARS-CoV-2 RNA results during periods of low prevalence, when there is a reduction in the predictive value of positive test results".<ref name="9Kblp">{{#invoke:Cite web||title=SARS-CoV-2 RNA testing: assurance of positive results during periods of low prevalence |url=https://www.gov.uk/government/publications/sars-cov-2-rna-testing-assurance-of-positive-results-during-periods-of-low-prevalence|access-date=19 September 2020|website=GOV.UK}}</ref>

=== Imaging ===
<noinclude>[[File:COVID19CTPneumonia.jpg|thumb|A [[Computed tomography|CT]] scan of a person with COVID-19 shows lesions (bright regions) in the lungs]]</noinclude>
[[File:COVID19CT1.webp|thumb|CT scan of rapid progression stage of COVID-19]]
[[File:COVID-19 Pneumonie - 82m Roe Thorax ap - 001.jpg|thumb|Chest X-ray showing COVID‑19 pneumonia]]

Chest CT scans may be helpful to diagnose COVID‑19 in individuals with a high clinical suspicion of infection but are not recommended for routine screening.<ref name="Salehi-2020" /><ref name="acr.org">{{#invoke:Cite web||date=22 March 2020|title=ACR Recommendations for the use of Chest Radiography and Computed Tomography (CT) for Suspected COVID-19 Infection|url=https://www.acr.org/Advocacy-and-Economics/ACR-Position-Statements/Recommendations-for-Chest-Radiography-and-CT-for-Suspected-COVID19-Infection|url-status=live|archive-url=https://web.archive.org/web/20200328055813/https://www.acr.org/Advocacy-and-Economics/ACR-Position-Statements/Recommendations-for-Chest-Radiography-and-CT-for-Suspected-COVID19-Infection|archive-date=28 March 2020|website=American College of Radiology}}</ref> Bilateral multilobar [[Ground-glass opacity|ground-glass opacities]] with a peripheral, asymmetric, and posterior distribution are common in early infection.<ref name="Salehi-2020" /><ref>{{#invoke:cite journal || vauthors = Pormohammad A, Ghorbani S, Khatami A, Razizadeh MH, Alborzi E, Zarei M, Idrovo JP, Turner RJ  | title = Comparison of influenza type A and B with COVID-19: A global systematic review and meta-analysis on clinical, laboratory and radiographic findings | journal = Reviews in Medical Virology | pages = e2179 | date = October 2020 | pmid = 33035373 | pmc = 7646051 | doi = 10.1002/rmv.2179 | s2cid = 222255245 | title-link = doi | volume = 31 | issue = 3 | doi-access = free }}</ref> Subpleural dominance, [[Crazy paving (medicine)|crazy paving]] (lobular septal thickening with variable alveolar filling), and [[Pulmonary consolidation|consolidation]] may appear as the disease progresses.<ref name="Salehi-2020" /><ref>{{#invoke:cite journal || vauthors = Lee EY, Ng MY, Khong PL | title = COVID-19 pneumonia: what has CT taught us? | journal = The Lancet. Infectious Diseases | volume = 20 | issue = 4 | pages = 384–385 | date = April 2020 | pmid = 32105641 | pmc = 7128449 | doi = 10.1016/S1473-3099(20)30134-1 | title-link = doi | doi-access = free }}</ref> Characteristic imaging features on chest [[radiographs]] and [[computed tomography]] (CT) of people who are symptomatic include asymmetric peripheral ground-glass opacities without [[pleural effusion]]s.<ref name="AJR">{{#invoke:cite journal || vauthors = Li Y, Xia L | title = Coronavirus Disease 2019 (COVID-19): Role of Chest CT in Diagnosis and Management | journal = AJR. American Journal of Roentgenology | volume = 214 | issue = 6 | pages = 1280–1286 | date = June 2020 | pmid = 32130038 | doi = 10.2214/AJR.20.22954 | s2cid = 212416282 }}</ref>

Many groups have created [[COVID‑19 datasets]] that include imagery such as the [[Italian Society of Medical and Interventional Radiology|Italian Radiological Society]] which has compiled an international online database of imaging findings for confirmed cases.<ref name="Cx70C">{{#invoke:Cite web||title=COVID-19 Database |url=https://www.sirm.org/category/senza-categoria/covid-19/ |website=Società Italiana di Radiologia Medica e Interventistica |access-date=11 March 2020 |language=it}}</ref> Due to overlap with other infections such as [[adenovirus]], imaging without confirmation by rRT-PCR is of limited [[Specificity (statistics)|specificity]] in identifying COVID‑19.<ref name="AJR" /> A large study in China compared chest CT results to PCR and demonstrated that though imaging is less specific for the infection, it is faster and more [[Sensitivity (statistics)|sensitive]].<ref name="jTxKm" />

=== Coding ===
In late 2019, the WHO assigned emergency [[ICD-10]] disease codes U07.1 for deaths from lab-confirmed SARS-CoV-2 infection and U07.2 for deaths from clinically or epidemiologically diagnosed COVID‑19 without lab-confirmed SARS-CoV-2 infection.<ref name="ICD10_2019_U07p2">{{#invoke:Cite web||year=2019|title=ICD-10 Version:2019|website=[[World Health Organization]] (WHO) |url=https://icd.who.int/browse10/2019/en#/U07.1|access-date=31 March 2020 |url-status=live|archive-url=https://archive.today/20200331004754/https://icd.who.int/browse10/2019/en%23/U07.1|archive-date=31 March 2020|quote=U07.2{{snd}}COVID-19, virus not identified{{snd}}COVID-19 NOS{{snd}}Use this code when COVID-19 is diagnosed clinically or epidemiologically but laboratory testing is inconclusive or not available. Use additional code, if desired, to identify pneumonia or other manifestations}}</ref>

=== Pathology ===
The main pathological findings at autopsy are:
* [[macroscopic scale|Macroscopy]]: [[pericarditis]], [[lung consolidation]] and [[pulmonary edema|pulmonary oedema]]<ref name="Cureus" />
* Lung findings:
** minor serous [[Exudate|exudation]], minor [[fibrin]] exudation<ref name="Cureus" />
** pulmonary oedema, [[pneumocyte]] [[hyperplasia]], large atypical [[pneumocyte]]s, interstitial [[inflammation]] with [[lymphocytic]] [[Infiltration (medical)|infiltration]] and [[giant cell|multinucleated giant cell]] formation<ref name="Cureus" />
** [[diffuse alveolar damage]] (DAD) with diffuse [[Pulmonary alveolus|alveolar]] [[exudates]]. DAD is the cause of [[acute respiratory distress syndrome]] (ARDS) and severe [[hypoxemia|hypoxaemia]].<ref name="Cureus" />
** [[healing|organisation]] of [[exudate]]s in [[Pulmonary alveolus|alveolar cavities]] and [[Pulmonary fibrosis|pulmonary interstitial fibrosis]]<ref name="Cureus" />
** [[plasma cell|plasmocytosis]] in [[bronchoalveolar lavage]] (BAL)<ref>{{#invoke:cite journal || vauthors = Giani M, Seminati D, Lucchini A, Foti G, Pagni F | title = Exuberant Plasmocytosis in Bronchoalveolar Lavage Specimen of the First Patient Requiring Extracorporeal Membrane Oxygenation for SARS-CoV-2 in Europe | journal = Journal of Thoracic Oncology | volume = 15 | issue = 5 | pages = e65–e66 | date = May 2020 | pmid = 32194247 | pmc = 7118681 | doi = 10.1016/j.jtho.2020.03.008 }}</ref>
* Blood and vessels: [[disseminated intravascular coagulation]] (DIC);<ref>{{#invoke:cite journal || vauthors = Lillicrap D | title = Disseminated intravascular coagulation in patients with 2019-nCoV pneumonia | journal = Journal of Thrombosis and Haemostasis | volume = 18 | issue = 4 | pages = 786–787 | date = April 2020 | pmid = 32212240 | pmc = 7166410 | doi = 10.1111/jth.14781 }}</ref> leukoerythroblastic reaction,<ref>{{#invoke:cite journal || vauthors = Mitra A, Dwyre DM, Schivo M, Thompson GR, Cohen SH, Ku N, Graff JP  | title = Leukoerythroblastic reaction in a patient with COVID-19 infection | journal = American Journal of Hematology | volume = 95 | issue = 8 | pages = 999–1000 | date = August 2020 | pmid = 32212392 | pmc = 7228283 | doi = 10.1002/ajh.25793 | title-link = doi | doi-access = free }}</ref> [[endotheliitis]],<ref name="SatturwarFowkes2021">{{#invoke:cite journal || vauthors = Satturwar S, Fowkes M, Farver C, Wilson AM, Eccher A, Girolami I, Pujadas E, Bryce C, Salem F, El Jamal SM, Paniz-Mondolfi A, Petersen B, Gordon RE, Reidy J, Fraggetta F, Marshall DA, Pantanowitz L  | title = Postmortem Findings Associated With SARS-CoV-2: Systematic Review and Meta-analysis | journal = The American Journal of Surgical Pathology | volume = 45 | issue = 5 | pages = 587–603 | date = May 2021 | pmid = 33481385 | doi = 10.1097/PAS.0000000000001650 | pmc = 8132567 | s2cid = 231679276 }}</ref> [[hemophagocytosis]]<ref name="SatturwarFowkes2021" />
* Heart: [[cardiac muscle cell]] necrosis<ref name="SatturwarFowkes2021" />
* Liver: microvesicular [[steatosis]]<ref name="Cureus" />
* Nose: [[Impact of COVID-19 on neurological, psychological and other mental health outcomes|shedding of olfactory epithelium]]<ref name="Meunier-2020" />
* Brain: [[Cerebral infarction|infarction]]<ref name="SatturwarFowkes2021" />
* Kidneys: acute tubular damage.<ref name="SatturwarFowkes2021" />
* Spleen: [[white pulp]] depletion.<ref name="SatturwarFowkes2021" />