Review Article
Laboratory diagnosis of COVID-19
a Universidade Federal do Rio de Janeiro (UFRJ), Faculdade de Medicina, Departamento de Pediatria, Rio de Janeiro, RJ, Brazil
b Universidade Federal do Rio de Janeiro (UFRJ), Instituto de Puericultura e Pediatria Martagão Gesteira (IPPMG), Rio de Janeiro, RJ, Brazil
c Sociedade Brasileira de Pediatria, Departamento Científico de Imunologia Clínica, Rio de Janeiro, RJ, Brazil
d Associação Brasileira de Alergia e Imunologia, Brazil
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A, A-lines, showing the “bat sign” (pattern A, healthy lung); B, B-line (with continuity of the pleura through the cartilaginous structure in young children); C, Coexistence of A-lines and B-lines in a single window; D, Several B-lines (B pattern, interstitial syndrome).</p>" ] ] ] "autores" => array:1 [ 0 => array:2 [ "autoresLista" => "Manuel Sobrino Toro, José Luis Vázquez Martínez, Ricardo Viana Falcão, Arnaldo Prata-Barbosa, Antonio José Ledo Alves da Cunha" "autores" => array:5 [ 0 => array:2 [ "nombre" => "Manuel Sobrino" "apellidos" => "Toro" ] 1 => array:2 [ "nombre" => "José Luis Vázquez" "apellidos" => "Martínez" ] 2 => array:2 [ "nombre" => "Ricardo Viana" "apellidos" => "Falcão" ] 3 => array:2 [ "nombre" => "Arnaldo" "apellidos" => "Prata-Barbosa" ] 4 => array:2 [ "nombre" => "Antonio José Ledo Alves da" "apellidos" => "Cunha" ] ] ] ] ] "idiomaDefecto" => "en" "EPUB" => "https://multimedia.elsevier.es/PublicationsMultimediaV1/item/epub/S0021755720301935?idApp=UINPBA000049" "url" => "/00217557/0000009700000001/v2_202102230657/S0021755720301935/v2_202102230657/en/main.assets" ] "itemAnterior" => array:19 [ "pii" => "S0021755720301868" "issn" => "00217557" "doi" => "10.1016/j.jped.2020.06.003" "estado" => "S300" "fechaPublicacion" => "2021-01-01" "aid" => "898" "copyright" => "Sociedade Brasileira de Pediatria" "documento" => "article" "crossmark" => 1 "licencia" => "http://creativecommons.org/licenses/by-nc-nd/4.0/" "subdocumento" => "sco" "cita" => "J Pediatr (Rio J). 2021;97:4-6" "abierto" => array:3 [ "ES" => true "ES2" => true "LATM" => true ] "gratuito" => true "lecturas" => array:1 [ "total" => 0 ] "en" => array:9 [ "idiomaDefecto" => true "cabecera" => "<span class="elsevierStyleTextfn">Editorial</span>" "titulo" => "“Changing the focus” for simulation-based education assessment… not simply “changing the view” with videolaryngoscopy" "tienePdf" => "en" "tieneTextoCompleto" => "en" "paginas" => array:1 [ 0 => array:2 [ "paginaInicial" => "4" "paginaFinal" => "6" ] ] "contieneTextoCompleto" => array:1 [ "en" => true ] "contienePdf" => array:1 [ "en" => true ] "autores" => array:1 [ 0 => array:2 [ "autoresLista" => "Vinay M. Nadkarni, Rodrigo J. Daly Guris, Ellen S. Deutsch" "autores" => array:3 [ 0 => array:2 [ "nombre" => "Vinay M." "apellidos" => "Nadkarni" ] 1 => array:2 [ "nombre" => "Rodrigo J." "apellidos" => "Daly Guris" ] 2 => array:2 [ "nombre" => "Ellen S." "apellidos" => "Deutsch" ] ] ] ] ] "idiomaDefecto" => "en" "EPUB" => "https://multimedia.elsevier.es/PublicationsMultimediaV1/item/epub/S0021755720301868?idApp=UINPBA000049" "url" => "/00217557/0000009700000001/v2_202102230657/S0021755720301868/v2_202102230657/en/main.assets" ] "en" => array:17 [ "idiomaDefecto" => true "cabecera" => "<span class="elsevierStyleTextfn">Review Article</span>" "titulo" => "Laboratory diagnosis of COVID-19" "tieneTextoCompleto" => true "paginas" => array:1 [ 0 => array:2 [ "paginaInicial" => "7" "paginaFinal" => "12" ] ] "autores" => array:1 [ 0 => array:3 [ "autoresLista" => "Ekaterini S. Goudouris" "autores" => array:1 [ 0 => array:4 [ "nombre" => "Ekaterini S." "apellidos" => "Goudouris" "email" => array:1 [ 0 => "egoudouris@gmail.com" ] "referencia" => array:4 [ 0 => array:2 [ "etiqueta" => "<span class="elsevierStyleSup">a</span>" "identificador" => "aff0005" ] 1 => array:2 [ "etiqueta" => "<span class="elsevierStyleSup">b</span>" "identificador" => "aff0010" ] 2 => array:2 [ "etiqueta" => "<span class="elsevierStyleSup">c</span>" "identificador" => "aff0015" ] 3 => array:2 [ "etiqueta" => "<span class="elsevierStyleSup">d</span>" "identificador" => "aff0020" ] ] ] ] "afiliaciones" => array:4 [ 0 => array:3 [ "entidad" => "Universidade Federal do Rio de Janeiro (UFRJ), Faculdade de Medicina, Departamento de Pediatria, Rio de Janeiro, RJ, Brazil" "etiqueta" => "a" "identificador" => "aff0005" ] 1 => array:3 [ "entidad" => "Universidade Federal do Rio de Janeiro (UFRJ), Instituto de Puericultura e Pediatria Martagão Gesteira (IPPMG), Rio de Janeiro, RJ, Brazil" "etiqueta" => "b" "identificador" => "aff0010" ] 2 => array:3 [ "entidad" => "Sociedade Brasileira de Pediatria, Departamento Científico de Imunologia Clínica, Rio de Janeiro, RJ, Brazil" "etiqueta" => "c" "identificador" => "aff0015" ] 3 => array:3 [ "entidad" => "Associação Brasileira de Alergia e Imunologia, Brazil" "etiqueta" => "d" "identificador" => "aff0020" ] ] ] ] "textoCompleto" => "<span class="elsevierStyleSections"><span id="sec0005" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0035">Introduction</span><p id="par0005" class="elsevierStylePara elsevierViewall">Since December 2019, humanity is once again facing a pandemic, this time caused by a betacoronavirus, the SARS-CoV-2. The disease caused by this infection was named coronavirus disease 2019 (COVID-19).<a class="elsevierStyleCrossRef" href="#bib0005"><span class="elsevierStyleSup">1</span></a></p><p id="par0010" class="elsevierStylePara elsevierViewall">SARS-CoV-2 is a respiratory transmitting virus that causes a flu-like condition and, in some cases, severe acute respiratory syndrome (SARS).<a class="elsevierStyleCrossRef" href="#bib0005"><span class="elsevierStyleSup">1</span></a> However, the follow-up of COVID-19 patients has shown that the virus is capable of causing symptoms outside the respiratory tract, in addition to complications of an inflammatory nature in several organs, expanding the spectrum of associated clinical manifestations.<a class="elsevierStyleCrossRef" href="#bib0010"><span class="elsevierStyleSup">2</span></a> Early and accurate diagnosis of SARS-CoV-2 infection is essential for prevention and pandemic containment. The heterogeneity of the clinical presentation, from asymptomatic individuals to severe cases, and the relevant diversity of non-specific clinical manifestations of COVID-19, reinforce the need for complementary tests with good sensitivity and specificity.<a class="elsevierStyleCrossRef" href="#bib0015"><span class="elsevierStyleSup">3</span></a> The results of diagnostic tests have serious implications: return to work of a health professional, transfer to a COVID-19 area of an inpatient unit, or the reverse, possible contamination of family members, among other delicate situations.</p><p id="par0015" class="elsevierStylePara elsevierViewall">As with any other infection, the gold standard for diagnosis is the identification of the infectious agent. In the case of viral infections, this identification can be made by visualizing viral particles at electron microscopy or identifying intracellular viral inclusions at light microscopy. Tissue cultures are necessary for the study of <span class="elsevierStyleItalic">in vitro</span> virus replication. These methods require technology that is usually available only in research centers. In commercial laboratories, immunoenzymatic assays or agglutination tests are available for detection of viral antigens and nucleic acid amplification tests for detection of virus genetic material.<a class="elsevierStyleCrossRefs" href="#bib0020"><span class="elsevierStyleSup">4,5</span></a></p><p id="par0020" class="elsevierStylePara elsevierViewall">An indirect way to diagnose viral infections is the identification of a specific immune system response. The humoral response, or antibody production, is the simplest way to diagnose infectious conditions. There are different techniques for identifying antibodies that are directed against different parts of viruses.<a class="elsevierStyleCrossRefs" href="#bib0020"><span class="elsevierStyleSup">4,5</span></a> However, it is important to note that the immune response to viral microorganisms occurs primarily by innate immunity, particularly by NK cells, and cellular immunity, especially cytotoxic T cells (TCD8+).<a class="elsevierStyleCrossRef" href="#bib0030"><span class="elsevierStyleSup">6</span></a></p><p id="par0025" class="elsevierStylePara elsevierViewall">To date, PubMed features over 35,000 articles on COVID-19. Many of them are presented as preprint, without peer review; some of these studies were conducted with poor methodology, providing unreliable results. Moreover, during the pandemic, knowledge has advanced greatly, and initially established concepts were modified, demonstrating that certain specificities of SARS-CoV-2 infection are not comparable with previously known viral infections.</p></span><span id="sec0010" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0040">Objectives</span><p id="par0030" class="elsevierStylePara elsevierViewall">This was a non-systematic review of the literature on the laboratory diagnosis of COVID-19, drawing attention to the knowledge already established, as well as the doubts that still need to be clarified.</p></span><span id="sec0015" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0045">Methods</span><p id="par0035" class="elsevierStylePara elsevierViewall">A non-systematic review of the literature was carried out in PubMed, searching for articles submitted in 2020, with the terms “diagnosis” OR “diagnostic” OR “tests” OR “diagnostic tests” AND “COVID-19” OR “SARS-CoV-2” in the title. Since many manuscripts have been made available in preprint version, without peer review, Google Scholar searches have also been performed, using the same terms.</p><p id="par0040" class="elsevierStylePara elsevierViewall">This study included articles in English, Portuguese, French, or Spanish, using the checklists proposed by the User's Guide to Medical Literature (JAMA Evidence) as inclusion criteria.<a class="elsevierStyleCrossRef" href="#bib0035"><span class="elsevierStyleSup">7</span></a></p></span><span id="sec0020" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0050">Results</span><p id="par0045" class="elsevierStylePara elsevierViewall">The complementary tests used in the diagnosis of COVID-19 can be divided into tests for etiological diagnosis and support tests, which help in the diagnosis or indicate the risk or presence of complications.</p><span id="sec0025" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0055">Tests for etiological diagnosis</span><p id="par0050" class="elsevierStylePara elsevierViewall">Tests for etiological diagnosis may be direct, identifying genetic material of SARS-CoV-2, or indirect, determining the humoral immune response to SARS-CoV-2.</p><p id="par0055" class="elsevierStylePara elsevierViewall">The most commonly used method for identifying genetic material from SARS-CoV-2 is real-time polymerase chain reaction (RT-PCR). This method involves reverse transcription of the genetic material of the virus (RNA) to complementary DNA (cDNA), followed by amplification of some regions of the cDNA. Probes (DNA/RNA marked sequences to identify the genetic target in the material) and primers (DNA/RNA sequences that promote replication of the genetic material found in the sample) were created after the SARS-CoV-2 genome was sequenced. Several serial amplification cycles are performed to identify these targets: the more cycles are needed, the lower the viral load of the material under study.<a class="elsevierStyleCrossRef" href="#bib0040"><span class="elsevierStyleSup">8</span></a></p><p id="par0060" class="elsevierStylePara elsevierViewall">Four regions of the SARS-CoV-2 genome have been targeted: RdRp gene (RNA-dependent RNA polymerase), genes from structural proteins E (virus envelope) and N (virus nucleocapsid), and ORF1ab gene (open reading frame 1a and 1b).<a class="elsevierStyleCrossRefs" href="#bib0015"><span class="elsevierStyleSup">3,8</span></a> Kits using different regions of the genome are commercially available. The sequential use of different probes and primers for the RdRp, E and N genes, known as the Charité-Berlin Institute protocol, presents good sensitivity and specificity.<a class="elsevierStyleCrossRef" href="#bib0045"><span class="elsevierStyleSup">9</span></a> There are other proposed protocols that follow the same logic of sequential use of probes and primes for different genetic targets.<a class="elsevierStyleCrossRef" href="#bib0050"><span class="elsevierStyleSup">10</span></a></p><p id="par0065" class="elsevierStylePara elsevierViewall">Regardless of the method used, the sensitivity and specificity of the different RT-PCR kits are not 100%. This is considered the gold standard for diagnosis of SARS-CoV-2 infection, but its sensitivity is estimated to be approximately 70% and specificity, 95%.<a class="elsevierStyleCrossRefs" href="#bib0055"><span class="elsevierStyleSup">11,12</span></a> Many factors can interfere with the results, whether related to the virus, to the method itself (the collection procedure and handling of the material), or even to the viral load of the sample (type of material collected, duration of symptoms, and disease severity).<a class="elsevierStyleCrossRef" href="#bib0065"><span class="elsevierStyleSup">13</span></a></p><p id="par0070" class="elsevierStylePara elsevierViewall">Mutations in the virus genome can render the probes and primers obsolete, producing false negative results. To date, SARS-CoV-2 has undergone mutations, but without implications for the RT-PCR detection. Mismatch between primers and probes can also lead to false negative results, and ideally more than one region of the virus genome should be simultaneously or sequentially amplified.<a class="elsevierStyleCrossRef" href="#bib0065"><span class="elsevierStyleSup">13</span></a></p><p id="par0075" class="elsevierStylePara elsevierViewall">Factors related to the collection procedure and handling of the material are often responsible for false negative results. Dacron or polyester swabs should be used and immersed immediately after collection in appropriate and refrigerated storage medium. The material should be kept under refrigeration and quickly sent to the laboratory.<a class="elsevierStyleCrossRefs" href="#bib0050"><span class="elsevierStyleSup">10,13</span></a></p><p id="par0080" class="elsevierStylePara elsevierViewall">A low viral load, usually found in asymptomatic individuals or in those with mild clinical conditions, may also be responsible for a false negative result.<a class="elsevierStyleCrossRefs" href="#bib0070"><span class="elsevierStyleSup">14,15</span></a> Individuals with more severe clinical conditions have greater elimination of viruses.<a class="elsevierStyleCrossRef" href="#bib0080"><span class="elsevierStyleSup">16</span></a> Although it has been described that there may be elimination of viruses from two to three days before to up to six weeks after the onset of symptoms,<a class="elsevierStyleCrossRef" href="#bib0040"><span class="elsevierStyleSup">8</span></a> very early (before three days of symptoms) or late material collection (after the seventh day) may produce false negative results, due to lower viral load.<a class="elsevierStyleCrossRefs" href="#bib0005"><span class="elsevierStyleSup">1,13,15</span></a> The type of material and the collection technique also interfere with the result. In several studies, bronchoalveolar lavage was the material with the highest positivity, followed by sputum, nasopharyngeal swabs, and nasal swabs. Oropharyngeal swabs did not present good positivity.<a class="elsevierStyleCrossRefs" href="#bib0075"><span class="elsevierStyleSup">15,17</span></a> The identification of genetic material of the virus in feces is less common and has uncertain significance, since infecting virus was not detected in this material.<a class="elsevierStyleCrossRef" href="#bib0090"><span class="elsevierStyleSup">18</span></a> Viral particles were not isolated in urine or blood.<a class="elsevierStyleCrossRef" href="#bib0090"><span class="elsevierStyleSup">18</span></a> Saliva tests have also been implemented, but have lower sensitivity than the nasopharyngeal swab and require validation.<a class="elsevierStyleCrossRef" href="#bib0095"><span class="elsevierStyleSup">19</span></a></p><p id="par0085" class="elsevierStylePara elsevierViewall">False positive results are most commonly related to errors in sample handling during or after swab collection, leading to inadvertent contamination.<a class="elsevierStyleCrossRef" href="#bib0065"><span class="elsevierStyleSup">13</span></a></p><p id="par0090" class="elsevierStylePara elsevierViewall">Tests to identify genetic material of the virus using simpler techniques, which do not require personal and sophisticated devices and that produce faster results, have been developed.<a class="elsevierStyleCrossRef" href="#bib0015"><span class="elsevierStyleSup">3</span></a> One example is the qualitative detection of the E and N proteins genes through the GeneXpert (Cepheid Company) platform, in which the amplification process takes place within a cartridge and provides results in 45 min.<a class="elsevierStyleCrossRef" href="#bib0100"><span class="elsevierStyleSup">20</span></a></p><p id="par0095" class="elsevierStylePara elsevierViewall">Point-of-care tests for SARS-CoV-2 proteins, most commonly using lateral flow assays, are useful for diagnosis in regions where there are no specialized laboratories.<a class="elsevierStyleCrossRefs" href="#bib0015"><span class="elsevierStyleSup">3,21</span></a></p><p id="par0100" class="elsevierStylePara elsevierViewall">The presence of genetic material in respiratory tract secretions has no direct relationship with virus viability or infectivity, since inactive or dead virus particles can be identified.<a class="elsevierStyleCrossRef" href="#bib0040"><span class="elsevierStyleSup">8</span></a> Therefore, a patient with positive RT-PCR test is not always able to infect other people. The viability of SARS-CoV-2 and consequent infectivity can be assessed directly, <span class="elsevierStyleItalic">in vitro</span>, by its ability to contaminate cells and, indirectly, through the threshold cycles (the lower the Ct, the higher the viral load) or identification of sub-genomic RNA (which are transcribed only by viable viruses).<a class="elsevierStyleCrossRef" href="#bib0090"><span class="elsevierStyleSup">18</span></a></p><p id="par0105" class="elsevierStylePara elsevierViewall">Serological tests identify the presence of humoral response to SARS-CoV-2. Antibodies of IgA, IgM, and IgG isotypes specific to different virus proteins are detected by enzyme-linked immunosorbent assay (ELISA) or chemiluminescence immunoassays (CLIA), and the latter has been shown to be more sensitive.<a class="elsevierStyleCrossRef" href="#bib0105"><span class="elsevierStyleSup">21</span></a> It is known that the priority immune response to the virus is related to the cytotoxic activity of NK cells and CD8 + T lymphocytes. There is evidence of robust cellular response to SARS-CoV-2, regardless of the results of serological tests;<a class="elsevierStyleCrossRef" href="#bib0110"><span class="elsevierStyleSup">22</span></a> however, tests to evaluate the specific cellular immune response for SARS-CoV-2 are not yet commercially available.</p><p id="par0110" class="elsevierStylePara elsevierViewall">Antibodies against S protein, where the receptor-binding domain (RBD) is located, are very specific for SARS-CoV-2;<a class="elsevierStyleCrossRef" href="#bib0050"><span class="elsevierStyleSup">10</span></a> their levels presented a good correlation with the virus's neutralization capacity.<a class="elsevierStyleCrossRef" href="#bib0115"><span class="elsevierStyleSup">23</span></a> However, the role of antibodies directed to other proteins in the pathogenesis of COVID-19, even promoting a greater penetration of the virus into cells, still need to be elucidated.<a class="elsevierStyleCrossRef" href="#bib0120"><span class="elsevierStyleSup">24</span></a></p><p id="par0115" class="elsevierStylePara elsevierViewall">Sensitivity and specificity of serological tests vary according to the testing technique, specificity of the antibody studied, duration of symptoms at the time of collection, and immunocompetence of the individual.<a class="elsevierStyleCrossRef" href="#bib0020"><span class="elsevierStyleSup">4</span></a> However, actual sensitivity and specificity values for these tests are difficult to define considering that a gold standard for diagnosis with high sensitivity is not yet available.<a class="elsevierStyleCrossRef" href="#bib0055"><span class="elsevierStyleSup">11</span></a> Most of the tests in use were not evaluated in scientific publications.<a class="elsevierStyleCrossRef" href="#bib0105"><span class="elsevierStyleSup">21</span></a></p><p id="par0120" class="elsevierStylePara elsevierViewall">The assessment of specific antibodies to N protein is more sensitive and less specific, since this protein is more abundant in coronaviruses. Antibodies directed to S protein are more specific to SARS-CoV-2, because in this protein is RDB.<a class="elsevierStyleCrossRef" href="#bib0040"><span class="elsevierStyleSup">8</span></a></p><p id="par0125" class="elsevierStylePara elsevierViewall">In addition, other factors that interfere with the results are duration of symptoms when the blood is collected and severity of the clinical picture. IgM is identified from the fifth day of symptomatology, and more significantly, from the eighth day onwards. The specific IgA dosage appears to be more sensitive and the values seem to increase earlier than those of IgM.<a class="elsevierStyleCrossRef" href="#bib0105"><span class="elsevierStyleSup">21</span></a> Specific IgG values begin to be detectable from the tenth day of symptom onset, and more significantly, from the 14th day onwards.<a class="elsevierStyleCrossRef" href="#bib0105"><span class="elsevierStyleSup">21</span></a> These tests are therefore not appropriate for the early diagnosis of COVID-19. They are, however, relevant when RT-PCR is not available or is negative in the face of a suggestive clinical picture, when the patient has been symptomatic for over 14 days,<a class="elsevierStyleCrossRefs" href="#bib0040"><span class="elsevierStyleSup">8,21</span></a> or to assist in the diagnosis of COVID-19-related multisystemic inflammatory syndrome.<a class="elsevierStyleCrossRef" href="#bib0125"><span class="elsevierStyleSup">25</span></a></p><p id="par0130" class="elsevierStylePara elsevierViewall">Some studies report patients with mild (or even asymptomatic) COVID-19 present lower levels of SARS-CoV-2-specific antibodies or may even do not develop detectable levels, while patients with more severe conditions have higher levels of these.<a class="elsevierStyleCrossRefs" href="#bib0130"><span class="elsevierStyleSup">26–28</span></a> These data raise questions about the protective capacity of antibodies and may suggest the participation of specific antibodies in the pathogenesis of COVID-19.<a class="elsevierStyleCrossRefs" href="#bib0070"><span class="elsevierStyleSup">14,24</span></a></p><p id="par0135" class="elsevierStylePara elsevierViewall">One study demonstrated that the positivity of serological tests was not accompanied by a rapid drop in virus elimination, which may indicate that the positivity of these tests does not necessarily imply prompt resolution of the disease or absence of infectivity.<a class="elsevierStyleCrossRef" href="#bib0090"><span class="elsevierStyleSup">18</span></a></p><p id="par0140" class="elsevierStylePara elsevierViewall">It has recently been shown that specific IgG levels suffer significant decline after two/three months.<a class="elsevierStyleCrossRef" href="#bib0135"><span class="elsevierStyleSup">27</span></a> Considering that the immune response to the virus is primarily cellular, it is not yet known what are the implications of this reduction in the protection against the virus.</p><p id="par0145" class="elsevierStylePara elsevierViewall">Regardless of the test used for diagnosis, either identification of genetic material of the virus or serologic test, the interpretation of the results is based on the accuracy of the test itself, and also on the estimated risk of the disease before the results. This risk is modified by the prevalence of COVID-19 in a given region.<a class="elsevierStyleCrossRef" href="#bib0055"><span class="elsevierStyleSup">11</span></a> This means that tests developed in regions where the prevalence of SARS-CoV-2 infection is high tend to have lower sensitivity when used in regions where the prevalence is lower.</p><p id="par0150" class="elsevierStylePara elsevierViewall">A single negative test in an individual with a characteristic clinical picture should not discard the possibility of COVID-19.<a class="elsevierStyleCrossRef" href="#bib0055"><span class="elsevierStyleSup">11</span></a> In turn, a positive RT-PCR has greater strength to confirm the diagnosis than a negative test has to discard it, since it presents high specificity, with only moderate sensitivity.<a class="elsevierStyleCrossRef" href="#bib0055"><span class="elsevierStyleSup">11</span></a></p><p id="par0155" class="elsevierStylePara elsevierViewall">Point-of-care tests for antibodies against SARS-CoV-2 using lateral flow assays (usually immunochromatography) are quite numerous and many of them have not been adequately validated.<a class="elsevierStyleCrossRef" href="#bib0100"><span class="elsevierStyleSup">20</span></a> Moreover, they were tested in the laboratory using plasma or serum, but have been applied with whole blood, which can greatly modify their sensitivity.<a class="elsevierStyleCrossRef" href="#bib0105"><span class="elsevierStyleSup">21</span></a> They are not recommended to be used for the individual diagnosis of COVID-19, but may be useful in implementing public policies.<a class="elsevierStyleCrossRef" href="#bib0145"><span class="elsevierStyleSup">29</span></a></p></span><span id="sec0030" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0060">Support tests</span><p id="par0160" class="elsevierStylePara elsevierViewall">These are laboratory or imaging tests that demonstrate characteristic manifestations of COVID-19, its complications, and/or risk factors for complications.</p><span id="sec0035" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0065">Laboratory tests</span><p id="par0165" class="elsevierStylePara elsevierViewall">Complete blood count – lymphopenia, eosinopenia, and neutrophil/lymphocyte ratio ≥ 3.13 are related to greater severity and worse prognosis. Thrombocytopenia is related to a higher risk of myocardial damage and a worse prognosis.<a class="elsevierStyleCrossRef" href="#bib0010"><span class="elsevierStyleSup">2</span></a> Lymphopenia results from a multifactorial mechanism that includes the cytopathic effect of the virus, induction of apoptosis, IL1-mediated pyroptosis, and bone marrow suppression by inflammatory cytokines.<a class="elsevierStyleCrossRef" href="#bib0150"><span class="elsevierStyleSup">30</span></a></p><p id="par0170" class="elsevierStylePara elsevierViewall">High values of C-reactive protein (CRP), ferritin, D-dimer, procalcitonin, lactic dehydrogenesis (DHL), prothrombin time, activated partial thromboplastin time, amyloid serum protein A, creatine kinase (CK), glutamic-pyruvic transaminase (SGPT), urea, and creatinine are risk factors for more severe disease, thromboembolic complications, myocardial damage, and/or worse prognosis.<a class="elsevierStyleCrossRefs" href="#bib0010"><span class="elsevierStyleSup">2,30–32</span></a></p><p id="par0175" class="elsevierStylePara elsevierViewall">Immunological markers that may also represent risk factors for greater severity and/or worse prognosis are: decreased values of CD4 + T and CD8+ lymphocytes, and NK cells and increased values of IL6, IL-8, IL-10, IFN-γ, TNF-IL-2R, TNF-α, GM-CSF, and IL-1 β.<a class="elsevierStyleCrossRefs" href="#bib0010"><span class="elsevierStyleSup">2,32</span></a></p></span><span id="sec0040" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0070">Imaging tests</span><p id="par0180" class="elsevierStylePara elsevierViewall">Imaging tests for the diagnosis of COVID-19 have gained relevance, given the unavailability of tests for etiological diagnosis.<a class="elsevierStyleCrossRef" href="#bib0015"><span class="elsevierStyleSup">3</span></a> The alterations described in these tests can also be found in influenza or mycoplasma infections, in inflammatory processes of different origins, or in eosinophilic lung diseases.<a class="elsevierStyleCrossRef" href="#bib0165"><span class="elsevierStyleSup">33</span></a> Although the findings in these tests are not specific to COVID-19, given a compatible clinical picture and/or the presence of confirmed or possible history of contact, they may help in the diagnosis.</p><p id="par0185" class="elsevierStylePara elsevierViewall">Plain chest X-rays are less sensitive than computed tomography, but may evidence sparse bilateral consolidations accompanied by ground glass opacities, peripheral/subpleural images, predominantly in the lower lobes.<a class="elsevierStyleCrossRef" href="#bib0165"><span class="elsevierStyleSup">33</span></a></p><p id="par0190" class="elsevierStylePara elsevierViewall">Computed tomography of the chest presents greater sensitivity and reveals multifocal, bilateral, peripheral/subpleural ground glass opacities, generally affecting the posterior portions of the lower lobes, with or without associated consolidations.<a class="elsevierStyleCrossRefs" href="#bib0165"><span class="elsevierStyleSup">33,34</span></a> Children have a similar presentation to that found in adults, albeit with a milder involvement.<a class="elsevierStyleCrossRef" href="#bib0165"><span class="elsevierStyleSup">33</span></a> The halo sign, described as a consolidation area involved by ground glass opacities, was identified in 50% of the children.<a class="elsevierStyleCrossRef" href="#bib0165"><span class="elsevierStyleSup">33</span></a> An inverted halo sign, in which areas of ground glass opacities are surrounded by condensation halo, has also been described.<a class="elsevierStyleCrossRef" href="#bib0175"><span class="elsevierStyleSup">35</span></a></p><p id="par0195" class="elsevierStylePara elsevierViewall">Pulmonary ultrasonography has good sensitivity; the typical findings are B-lines, consolidations and pleural thickening.<a class="elsevierStyleCrossRef" href="#bib0180"><span class="elsevierStyleSup">36</span></a> The advantages of this method are its lower cost, absence of radiation exposure, and the fact that it does not require sedation or transportation of unstable patients.<a class="elsevierStyleCrossRef" href="#bib0185"><span class="elsevierStyleSup">37</span></a></p><p id="par0200" class="elsevierStylePara elsevierViewall">Most studies on diagnostic methods presented here refer to adults; however, studies specific to the pediatric age group show very similar data.<a class="elsevierStyleCrossRef" href="#bib0190"><span class="elsevierStyleSup">38</span></a></p><p id="par0205" class="elsevierStylePara elsevierViewall">The data presented suggest that the diagnosis of COVID-19 should be based on clinical manifestations, contact history, imaging tests, laboratory tests, and not only on serological tests and the search for the genetic material of the virus. In addition, strategies to increase sensitivity, specificity, and speed of diagnosis are fundamental.<a class="elsevierStyleCrossRef" href="#bib0055"><span class="elsevierStyleSup">11</span></a></p></span></span></span><span id="sec0045" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0075">Conclusions</span><p id="par0210" class="elsevierStylePara elsevierViewall">The gold standard for the diagnosis of SARS-CoV-2 infection is the identification of viral genetic material by RT-PCR, in different samples, with greater sensitivity in bronchoalveolar lavage and nasopharyngeal swab. Many factors related to the individual, the collection procedure, and the test technique interfere with the sensitivity of these tests. Therefore, a negative test in a patient with a characteristic clinical picture should not discard the possibility of COVID-19.</p><p id="par0215" class="elsevierStylePara elsevierViewall">The available serological tests are different from each other and many factors influence their sensitivity and specificity. Not all patients who have SARS-CoV-2 infection will have detectable levels of antibodies, particularly if they have milder symptoms. The absence of antibodies does not imply the absence of contact or protection against the virus, since there may be an efficient specific cellular immune response. In turn, the presence of antibodies does not rule out the possibility that the individual is still infectious, as no immediate reduction in the elimination of the virus has been identified.</p><p id="par0220" class="elsevierStylePara elsevierViewall">The support laboratory and imaging tests show alterations that are characteristic of COVID-19, but they lack specificity.</p><p id="par0225" class="elsevierStylePara elsevierViewall">The diagnosis of COVID-19 should be based on clinical and epidemiological history, tests for etiological diagnosis, and tests to support the diagnosis of infection and/or its complications.</p><p id="par0230" class="elsevierStylePara elsevierViewall">New diagnostic methods with higher sensitivity and specificity, as well as faster results, are necessary and are being developed.</p></span><span id="sec0050" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0080">Conflicts of interest</span><p id="par0235" class="elsevierStylePara elsevierViewall">The author declares no conflicts of interest.</p></span></span>" "textoCompletoSecciones" => array:1 [ "secciones" => array:9 [ 0 => array:3 [ "identificador" => "xres1469371" "titulo" => "Abstract" "secciones" => array:4 [ 0 => array:2 [ "identificador" => "abst0005" "titulo" => "Objectives" ] 1 => array:2 [ "identificador" => "abst0010" "titulo" => "Data sources" ] 2 => array:2 [ "identificador" => "abst0015" "titulo" => "Summary of findings" ] 3 => array:2 [ "identificador" => "abst0020" "titulo" => "Conclusions" ] ] ] 1 => array:2 [ "identificador" => "xpalclavsec1338388" "titulo" => "Keywords" ] 2 => array:2 [ "identificador" => "sec0005" "titulo" => "Introduction" ] 3 => array:2 [ "identificador" => "sec0010" "titulo" => "Objectives" ] 4 => array:2 [ "identificador" => "sec0015" "titulo" => "Methods" ] 5 => array:3 [ "identificador" => "sec0020" "titulo" => "Results" "secciones" => array:2 [ 0 => array:2 [ "identificador" => "sec0025" "titulo" => "Tests for etiological diagnosis" ] 1 => array:3 [ "identificador" => "sec0030" "titulo" => "Support tests" "secciones" => array:2 [ 0 => array:2 [ "identificador" => "sec0035" "titulo" => "Laboratory tests" ] 1 => array:2 [ "identificador" => "sec0040" "titulo" => "Imaging tests" ] ] ] ] ] 6 => array:2 [ "identificador" => "sec0045" "titulo" => "Conclusions" ] 7 => array:2 [ "identificador" => "sec0050" "titulo" => "Conflicts of interest" ] 8 => array:1 [ "titulo" => "References" ] ] ] "pdfFichero" => "main.pdf" "tienePdf" => true "fechaRecibido" => "2020-07-30" "fechaAceptado" => "2020-08-12" "PalabrasClave" => array:1 [ "en" => array:1 [ 0 => array:4 [ "clase" => "keyword" "titulo" => "Keywords" "identificador" => "xpalclavsec1338388" "palabras" => array:5 [ 0 => "Diagnosis" 1 => "Diagnostic tests" 2 => "Diagnostic techniques and procedures" 3 => "COVID-19" 4 => "Coronavirus" ] ] ] ] "tieneResumen" => true "resumen" => array:1 [ "en" => array:3 [ "titulo" => "Abstract" "resumen" => "<span id="abst0005" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0010">Objectives</span><p id="spar0005" class="elsevierStyleSimplePara elsevierViewall">This was a non-systematic review of the literature on the laboratory diagnosis of COVID-19.</p></span> <span id="abst0010" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0015">Data sources</span><p id="spar0010" class="elsevierStyleSimplePara elsevierViewall">Searches in PubMed and Google Scholar for articles made available in 2020, using the terms “diagnosis” OR “diagnostic” OR “diagnostic tests” OR “tests” AND “COVID-19” OR “SARS-CoV-2” in the title.</p></span> <span id="abst0015" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0020">Summary of findings</span><p id="spar0015" class="elsevierStyleSimplePara elsevierViewall">Tests for the etiological agent identify genetic material of SARS-CoV-2 or humoral responses to it. The gold standard for diagnosis is the identification of viral genome targets by real-time polymerase chain reaction (RT-PCR) in respiratory tract materials during the first week of symptoms. Serological tests should be indicated from the second week of symptoms onwards. A wide range of different tests is available, with variable sensitivity and specificity, most of which require validation. Laboratory tests such as complete blood count, C-reactive protein (CRP), D-dimer, clotting tests, lactic dehydrogenase (LDH), ferritin, and procalcitonin identify risk of disease with greater severity, thromboembolic complications, myocardial damage, and/or worse prognosis. Imaging tests may be useful for diagnosis, especially when there is a compatible clinical picture, and other tests presented negative results or were unavailable.</p></span> <span id="abst0020" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle" id="sect0025">Conclusions</span><p id="spar0020" class="elsevierStyleSimplePara elsevierViewall">The identification of genetic material of the virus by RT-PCR is the gold standard test, but its sensitivity is not satisfactory. The diagnosis of COVID-19 should be based on clinical data, epidemiological history, tests for etiological diagnosis, and tests to support the diagnosis of the disease and/or its complications. New diagnostic methods with higher sensitivity and specificity, as well as faster results, are necessary.</p></span>" "secciones" => array:4 [ 0 => array:2 [ "identificador" => "abst0005" "titulo" => "Objectives" ] 1 => array:2 [ "identificador" => "abst0010" "titulo" => "Data sources" ] 2 => array:2 [ "identificador" => "abst0015" "titulo" => "Summary of findings" ] 3 => array:2 [ "identificador" => "abst0020" "titulo" => "Conclusions" ] ] ] ] "NotaPie" => array:1 [ 0 => array:2 [ "etiqueta" => "☆" "nota" => "<p class="elsevierStyleNotepara" id="npar0005">Please cite this article as: Goudouris ES. Laboratory diagnosis of COVID-19. 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| Year/Month | Html | Total | |
|---|---|---|---|
| 2024 November | 7 | 6 | 13 |
| 2024 October | 30 | 36 | 66 |
| 2024 September | 46 | 29 | 75 |
| 2024 August | 49 | 50 | 99 |
| 2024 July | 56 | 43 | 99 |
| 2024 June | 35 | 18 | 53 |
| 2024 May | 38 | 16 | 54 |
| 2024 April | 43 | 27 | 70 |
| 2024 March | 49 | 27 | 76 |
| 2024 February | 50 | 30 | 80 |
| 2024 January | 34 | 37 | 71 |
| 2023 December | 36 | 31 | 67 |
| 2023 November | 50 | 41 | 91 |
| 2023 October | 40 | 43 | 83 |
| 2023 September | 37 | 40 | 77 |
| 2023 August | 33 | 27 | 60 |
| 2023 July | 30 | 14 | 44 |
| 2023 June | 27 | 20 | 47 |
| 2023 May | 43 | 19 | 62 |
| 2023 April | 33 | 14 | 47 |
| 2023 March | 67 | 28 | 95 |
| 2023 February | 47 | 23 | 70 |
| 2023 January | 42 | 29 | 71 |
| 2022 December | 83 | 30 | 113 |
| 2022 November | 59 | 32 | 91 |
| 2022 October | 92 | 47 | 139 |
| 2022 September | 75 | 47 | 122 |
| 2022 August | 108 | 45 | 153 |
| 2022 July | 97 | 59 | 156 |
| 2022 June | 121 | 43 | 164 |
| 2022 May | 83 | 37 | 120 |
| 2022 April | 112 | 69 | 181 |
| 2022 March | 105 | 55 | 160 |
| 2022 February | 43 | 29 | 72 |
| 2022 January | 84 | 30 | 114 |
| 2021 December | 41 | 60 | 101 |
| 2021 November | 45 | 45 | 90 |
| 2021 October | 50 | 27 | 77 |
| 2021 September | 46 | 26 | 72 |
| 2021 August | 52 | 25 | 77 |
| 2021 July | 65 | 25 | 90 |
| 2021 June | 136 | 31 | 167 |
| 2021 May | 359 | 42 | 401 |
| 2021 April | 953 | 100 | 1053 |
| 2021 March | 580 | 94 | 674 |
| 2021 February | 238 | 76 | 314 |
| 2021 January | 523 | 152 | 675 |
| 2020 December | 47 | 11 | 58 |
| 2020 November | 44 | 28 | 72 |
| 2020 October | 33 | 12 | 45 |
| 2020 September | 58 | 26 | 84 |
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