|Ahead of print publication
Rapid antigen test for COVID-19: A useful weapon in the arsenal of public health
Anurag Chaudhary, Priya Bansal, Mahesh Satija, Vikram K Gupta
Department of Community Medicine, Old Campus, Dayanand Medical College and Hospital (DMCH), Ludhiana, Punjab, India
|Date of Submission||02-Dec-2021|
|Date of Decision||05-Feb-2022|
|Date of Acceptance||22-Feb-2022|
Department of Community Medicine, Old Campus, Near Dandi Swami Chowk, Dayanand Medical College and Hospital (DMCH), Ludhiana - 141 001, Punjab, Ludhiana
Source of Support: None, Conflict of Interest: None
Rapid antigen test has a very important value as one of tools to address the Covid pandemic. Though this test is not as accurate as polymerase chain reaction (PCR) testing. As viral antigen appears before antibody formation in infected person. It is a specific marker of virus. Therefore, for detection of this highly infectious disease at an early stage, viral antigen testing can be a useful strategy in scenario of community transmission to prevent further spread. In India an advisory was issued by ICMR (on 14th June 2020) regarding usage of RAT for quick detection of COVID-19 positive patients. During second wave, Rapid antigen testing was advised only in symptomatic individuals and immediate contacts of laboratory confirmed positive cases. Though no test is perfect when it comes to the attributes of accuracy, accessibility, affordability, and timeliness of results. However, Rapid antigen test can be used as a useful test in public health that can benefit the larger population in breaking the chain of transmission if used wisely in different settings and according to the timeline of symptoms.
Keywords: Antigen test, COVID-19 screening test, point of care tests, SARS-CoV-2 testing.
|How to cite this URL:|
Chaudhary A, Bansal P, Satija M, Gupta VK. Rapid antigen test for COVID-19: A useful weapon in the arsenal of public health. Med J DY Patil Vidyapeeth [Epub ahead of print] [cited 2022 Dec 7]. Available from: https://www.mjdrdypv.org/preprintarticle.asp?id=343496
| Introduction and Background|| |
COVID-19 pandemic has taught important lessons to the medical fraternity over the last 1 and 1/2 years and still continuing. India experienced the first wave during August, September, and October 2020 and the second wave during April, May, and June 2021. One of the common features observed during both the waves was increased load on diagnostic facilities with a surge in the number of cases.
One of the first lines of defense against COVID-19 is its testing. It enables early identification and isolation of cases to decrease transmission. It also helps in targeting those who need care. This results in smooth health system functioning. During the early period of the pandemic, the nucleic acid amplification technique (NAAT) was developed, and hundreds of millions of tests were conducted worldwide. However, NAAT requires sophisticated laboratory infrastructure and skilled staff to perform tests. Therefore, timely and accurate testing is the need of the hour.
PubMed databases and the Indian Council of Medical Research (ICMR) website were searched to gather information on the use of rapid antigen tests in the screening/diagnosis of COVID19 from the onset of the COVID-19 epidemic to September 2021. Keywords “Point of care test OR Antigen test OR COVID-19 screening test OR SARS-CoV-2 testing AND community-based AND “2020” [DatePublication]: “2021” [DatePublication] were used for searching the articles. Also, official guidelines by the Indian Council of Medical Research, commentary, communications, and medical news were also explored for information regarding rapid antigen testing used in the screening of COVID19. All articles retrieved with different keywords were compiled and checked for duplication by the authors independently.
Original articles related to community-based cross-sectional studies, from the onset of COVID-19 pandemic to September 2021, whose full text was available and preferably in the English language were included [Table 1]. The systematic search yielded 210 articles, of which 23 were considered for further analysis, whereas seven were excluded from the initial analysis as they did not satisfy the inclusion criteria. Articles specifically discussing RT-PCR or serological tests were excluded. Articles not in the English language were also excluded. Any discrepancies or doubts regarding the exclusion criteria were resolved by mutual consensus. Finally, sixteen articles were selected for analysis [Figure 1].
|Table 1: Assessing the use of Rapid antigen testing as a useful tool in the public health field|
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| Need for Rapid Antigen Testing|| |
Testing is one of the main steps towards efforts for the prevention of viral transmission in the community. Real-time reverse transcription-polymerase chain reaction (rRT-PCR) and rapid antigen testing (RAT) are two diagnostic tests available for testing. Skilled technicians and sophisticated Biosafety level (BSL)- 2/BSL-3 laboratory setup is required to run the test and for results interpretation of RT-PCR testing. Moreover, sample collection and reporting of results requires a minimum of 8–10 hours. Small town and cities lack such sophisticated laboratories. Serological antibody tests were introduced, but they were not found suitable for diagnosis as these antibodies only appear after 2 weeks of the onset of symptoms. With this background, there was a need to develop a reliable point of care rapid antigen test (RAT).
With the introduction of RAT, it was expected that antigen-detecting rapid diagnostic tests (Ag-RDTs) will greatly expand access to testing, enabling the most accurate estimates of disease burden and targeting of control measures and treatments. Rapid tests being a type of lateral flow tests detect antigenic protein. This test is different from other medical tests that detect antibodies (antibody tests) or nucleic acid (nucleic acid tests) of either laboratory or point-of-care types. These tests can be implemented quickly with minimal training and offer significant cost advantages as compared to existing forms of polymerase chain reaction (PCR) testing. The result are easy to observe with the naked eye and available to users within 5–30 min. They have found their best use as part of mass testing or population-wide screening approaches.
| Timeline for Using Rapid Antigen Testing in India|| |
In India, an advisory was issued by the Indian Council of Medical Research (ICMR) (on 14th June 2020) regarding the usage of RAT for quick detection of COVID-19 positive patients. In combination with the gold standard RTPCR test, a standard Q COVID-19 Ag detection kit was recommended to be used as a point of care diagnostic assay for testing in particular settings. The settings included containment zones, health care facilities that included testing to be done on symptomatic patients as well asymptomatic patients getting hospitalized for emergency or elective procedures.
Another advisory was issued on 4th September 2020 by the ICMR regarding the strategy for COVID-19 testing in India. Rapid antigen test was recommended as the choice of test for routine surveillance in containment zones and screening at point of entry. Rapid antigen test was recommended as the first choice test for routine surveillance in nanocontainment areas and asymptomatic high risk contacts (family, workplace, elderly, and those with comorbidities). This advisory was issued in response to an increase in a number of cases during the first wave. During the second wave, another advisory was released by the ICMR regarding COVID-19 home testing using rapid antigen testing on 19/5/2021. Rapid antigen testing was advised only in symptomatic individuals and immediate contacts of laboratory-confirmed positive cases.
Standard Q COVID-19 Ag detection assay by SD Biosensor was made available in India during the first wave, and the following agencies evaluated it independently:
- Indian Council of Medical Research, Delhi; and
- All India Institute of Medical Sciences, Delhi
Standard Q COVID-19 Ag rapid antigen detection test has the advantage of very high specificity (i.e. ability to find out true negatives) which ranged from 99.3% to 100% at the two sites. While the sensitivity of the test (i.e. ability to detect true positives) varied from 50.6% to 84% in two independent evaluations, depending upon the viral load of the patient. Higher viral load correlated with higher sensitivity.
| Avantages|| |
Identification of asymptomatic
The appearance of symptoms in a person acts as a trigger for getting himself/herself tested or visiting a hospital. However, in case of the absence of symptoms, there is no such trigger therefore the person unknowingly keeps on transmitting the disease to family members and people at the workplace. Therefore, during the community transmission phase of the pandemic, it is very important to identify asymptomatic persons specifically in community settings to prevent further transmission by using this test. This will make work environments safer for everyone.
Advantages in various prevalence settings
The yield of this test always remains best in the case when a large number of people are reporting in the hospital with symptoms. The positive predictive value of the test increases with the high prevalence of disease in the community; therefore, the test can be of immense help during the phase of community transmission. However, it is preferable to use the RTPCR test in case few people are becoming positive in the community.
Advantages for various groups
People at the workplace get benefitted from this test as asymptomatic positive cases can be promptly isolated within a short period of time and therefore making the work environment safer for others. Similarly, weekly testing has been recommended for schools, universities, and health care facilities so that the normal routine working can be maintained.
| Challenges|| |
Testing in rural areas
There are many challenges associated with the usage of this test in certain settings like rural areas, particularly in absence of community participation and acceptance by the people. However, community acceptance can be obtained by convincing them by local leaders. The biggest advantage of using this test in rural areas is the test can be performed in a community setting in absence of a laboratory, and a trained local technician can collect the nasopharyngeal swab and perform the test with the result in just 20 min followed by isolation of a positive individual.
Home based testing
Home-based testing kit (Coviself) was introduced in the market in the month of May 2021 in India during the second wave. However, the acceptance of this kit by the people and the data of its usage are not available. Home-based testing kit has got the advantage of testing oneself in a home environment. However, the isolation on the part of the individual in case of testing positive is doubtful and risky in case the person decides to carry on his or her routine activities without isolation from the family and the workplace.
Diagnosing emerging variants
With the emergence of new variants during this pandemic, it is difficult to predict whether the new variants escape the rapid antigen testing.
Acceptance of the reliability of the test by medical personnel and general public
The sensitivity and specificity of the test are doubted by the medical personnel as well as the general population. It is very important to convince the medical personnel regarding its usage under specific circumstances wisely, keeping in mind the benefits of isolating the positive person promptly as a comparison to the same isolation occurring after 24 h of giving a sample, when the damage of affecting the family members or colleagues is already done.
| Recommendations|| |
Timing of various tests
COVID-19 studies,, showed that the virus can be cultured from patients within the first 8 days after symptom onset. This corresponds to the manufacturers' recommendations that within the first 5–7 days after symptom onset, Ag-RDTs can be used. COVID-19 patients after the onset of symptoms can remain RNA positive for 2–3 weeks. However, the antigen remains undetectable for 7–8 days after symptom onset, which coincides with the infectious period of the COVID-19 patient. Hence, for efficient testing, the duration of the timing of symptoms is very crucial. The benefits of all the tests can be reaped by utilizing them according to the appearance of symptoms in the individual. During the first week, RAT is recommended followed by RTPCR in the second week and serology test from the third week.
Testing kiosks in rural areas/special settings
Building diagnostic kiosks in rural areas can benefit the rural population in detecting positive cases and controlling the transmission.
Weekly testing in special settings/factories/universities can be done for safer working environments and to continue with routine activities.
| Conclusion|| |
No test is perfect when it comes to the attributes of accuracy, accessibility, affordability, and timeliness of results. However, the advantages of rapid antigen test as discussed can benefit the larger population and laboratories if used wisely in different settings like community transmission phase and according to the timeline of symptoms.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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