The current variants of caused by novel coronavirus disease (COVID-19) across the world alarming health authorities to conduct rapid screening and diagnostic tests. Swab specimens have been widely collected for initial diagnosis of novel coronavirus (COVID-19). Especially, for most vulnerable groups like people who staying abroad, they are in need to travel to other countries. As of this, public health authorities are aim to performing simultaneous tests with nasopharyngeal swab specimens including both antigen and RT-PCR tests for people in airports. This article aims to provide description on different anti covid tests and its procedures.
It is well-known that the novel coronavirus disease (COVID-19) is become an emergency day after day and has caused about 2.3 million deaths across the world. It is caused by Severe Acute Respiratory Syndrome-Corona Virus-2 (SARS-CoV-2) and in the early stages of this virus, Italy is the worst pandemic hit nation after China1. Although the condition is stabilised in this country, the rise of the second wave in some EU nations including Italy keeps alarming health authorities. The WHO and epidemiologists are mentioning that rapid and precise identification of this disease can limit the virus spreading, and early identification of infected persons can play a vital role in controlling its further escalation. The current best quality level of testing is the nasopharyngeal swab technique2.
SARS-CoV-2 can be communicated from human to human. The current theory is that the main transmission happened among bats and a yet-to-be-resolved transitional host animal3. It is assessed that a SARS-CoV-2 contaminated individual will transmit the virus to nearly three new persons (the regenerative number (R0)has arrived at the midpoint to be 3.28)4. The signs or symptoms can be varied from person to person, with certain patients staying asymptomatic, while others present with fever, exhaustion, cough, and a group of different symptoms. The COVID-19 side effects might be like patients with flu or regular viral infection. At this stage, the most probable method of transmission is believed to be through physical contact and air droplets released from the patient when coughing or talking. A research study presented a look at surface stability and aerosols of SARS-CoV-2 indicated that the infection might be found in vaporizers with thickness <5 μm for in any event up to 3 h and might be steadier on plastic and treated steel than on copper and cardboard5.
Due to the immediate spread of COVID-19 as it becoming the first breakthrough revolution in the field of disease detection and testing6. By enabling the immediate application of mitigation measures such as contact tracing, case identification, and rapid testing, some countries successfully limit the severity of COVID-19 disease. In Italy, the coronavirus testing strategy is increasing in terms of samples analysedevery week. The scientific-technical board (CTS) of the Government and local governments (Regions) that counsel on recent outbreak principles have agreed to proceed with nationwide testing. To control the further rise of SARS-CoV-2, Italian authorities have also approved customised rapid airport-style tests in random places.
Figure 1. The difference between tests for COVID-19
Testing involves the insertion of nasopharyngeal swabs of 6-inch long into the cavity between the inferior concha and vertebral of the nasopharyngeal pit. Then swab was rotated for 15 seconds multiple times. The test was directed in just a single nostril for everyone. After testing, the nasal was placed in a 20ml tube of 4ml saline and the nasopharyngeal swab placed 3 ml of the infection transport medium (Cepheid). The swab specimens were taken simultaneously and tests are conducted by the extraction of the viral RNA and ensuing intensification by real-time PCR. The test examines the extracted sample for explicit groupings of the genome of the SARS-CoV-2 infection, under WHO rules7.
The literature published on COVID-19 diagnostic tests majorly focused on healthcare workers, hospitalised patients, other epidemiological backgrounds. All countries have largely conducted the COVID-19 tests since the middle of the year 2020. Many health officials are recommending a test if a person is experiencing symptoms8. However, most of the testing involves nasopharyngeal swab samplesthrough quantitative RT-qPCR tests that produced relatively negative outcomes of SARS-CoV-2 infections. The limitation of these studies is that there is no precise measure of finding accuracy9. False-negative tests can lead people to have more relaxation and delay in treatment, whereas false positives can affect needless anxiety and make people unnecessary isolated.
Compared to protein-based testing, nucleic acid-based detection is more accurate. Swab tests done through antigens can reveal that if a person has been exposed to the virus. Antigen tests generally identify proteins or glycans, for example, the spike proteins found on the outside of the SARS-CoV-2 infection. The antigen test works by distinguishing explicit particles on the virus outer parts. This is similar to the rapid strep throat tests are finished. Patients are normally ready to get the aftereffects of rapid tests in as fast as 15 minutes or two or three hours.Porte L et al. (2020) reported that the rapid antigen detection tests (RDT) have produced high specificity and sensitivity in samples collected during initial 7-day symptoms and high viral load. These tests can be important for the early diagnosis of COVID-19 during the situation of limited access for molecular (nucleic acid) methods10. However, the rapid antigen tests are less precise than PCR tests, additionally, they are bound to yield a bogus negative outcome. Special attention is given to these tests in recent times are given to antigen testing to distinguish contaminated individuals at the earliest stage and diminish the odds for high virus speared11.
The study conducted by Wang X et al. (2020) has presented the comparison between both oropharyngeal and nasopharyngeal swab specimens for SARS-CoV-2 infection among 353 patients including both men and women12. Higher positive results were appearing in male patients than in female patients. Detection with nasopharyngeal specimens slightly hasa higher positive rate than oropharyngeal specimens. Nasopharyngeal swab tests produced higher positive rates than oropharyngeal swab tests at the new second wave outbreak of COVID-19.
1. Chintalapudi N, Battineni G, Sagaro GG, Amenta F. COVID-19 outbreak reproduction number estimations and forecasting in Marche, Italy. Int J Infect Dis. Published online 2020. doi:10.1016/j.ijid.2020.05.029
2. Tang YW, Schmitz JE, Persing DH, Stratton CW. Laboratory diagnosis of COVID-19: Current issues and challenges. J Clin Microbiol. Published online 2020. doi:10.1128/JCM.00512-20
3. Zhou P, Yang X Lou, Wang XG, et al. A pneumonia outbreak associated with a new coronavirus of probable bat origin. Nature. Published online 2020. doi:10.1038/s41586-020-2012-7
4. Liu Y, Gayle AA, Wilder-Smith A, Rocklöv J. The reproductive number of COVID-19 is higher compared to SARS coronavirus. J Travel Med. Published online 2020. doi:10.1093/jtm/taaa021
5. van Doremalen N, Bushmaker T, Morris DH, et al. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. N Engl J Med. Published online 2020. doi:10.1056/nejmc2004973
6. Péré H, Péré H, Péré H, et al. Nasal swab sampling for SARS-CoV-2: A convenient alternative in times of nasopharyngeal swab shortage. J Clin Microbiol. Published online 2020. doi:10.1128/JCM.00721-20
7. Corman VM, Landt O, Kaiser M, et al. Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR. Eurosurveillance. 2020;25(3):1-8. doi:10.2807/1560-7917.ES.2020.25.3.2000045
8. Lafond KE, Nair H, Rasooly MH, et al. Global Role and Burden of Influenza in Pediatric Respiratory Hospitalizations, 1982–2012: A Systematic Analysis. PLoS Med. 2016;13(3). doi:10.1371/journal.pmed.1001977
9. Robert H. Shmerling M. Which test is best for COVID-19? - Harvard Health Blog - Harvard Health Publishing. Accessed October 1, 2020. https://www.health.harvard.edu/blog/which-test-is-best-for-covid-19-2020081020734
10. Porte L, Legarraga P, Vollrath V, et al. Evaluation of a novel antigen-based rapid detection test for the diagnosis of SARS-CoV-2 in respiratory samples. Int J Infect Dis. Published online 2020. doi:10.1016/j.ijid.2020.05.098
11. Dinnes J, Deeks JJ, Adriano A, et al. Rapid, point-of-care antigen and molecular-based tests for diagnosis of SARS-CoV-2 infection. Cochrane Database Syst Rev. Published online 2020. doi:10.1002/14651858.CD013705
12. Wang X, Tan L, Wang X, et al. Comparison of nasopharyngeal and oropharyngeal swabs for SARS-CoV-2 detection in 353 patients received tests with both specimens simultaneously. Int J Infect Dis. Published online 2020. doi:10.1016/j.ijid.2020.04.023