Introduction
The novel coronaviruses belong to the β genus. COVID-19 is an acute respiratory infectious disease. People are generally susceptible. Currently, the patients infected by the novel coronavirus are the main source of infection; asymptomatic infected people can also be an infectious source. Based on the current epidemiological investigation, the incubation period is 1 to 14 days, mostly 3 to 7 days. The main manifestations include fever, fatigue and dry cough. Nasal congestion, runny nose, sore throat, myalgia and diarrhea are found in a few cases.
The COVID-19 Antigen Rapid Test Device (Colloidal Gold) is a rapid visual immunoassay for the qualitative, presumptive detection of COVID-19 antigens from throat swab, nasopharyngeal swab and nasal swab specimens. The test is intended for use as an aid in the rapid differential diagnosis of acute COVID-19 virus infection.
Test Principle
In COVID-19 antigen rapid test, the membrane is pre-coated with anti-COVID-19 antibodies on the test line region of the test. During testing, the diluted specimen reacts with the particle coated with anti-COVID-19 antibodies. The mixture migrates upward on the membrane by capillary action to react with anti-COVID-19 antibodies on the membrane and generate a colored line. The presence of this colored line in the test region indicates a positive result, while its absence indicates a negative result. To serve as a procedural control, a colored line will always appear in the control line region indicating that proper volume of specimen has been added and membrane wicking has occurred.
Illustrations Figure
As shown in Figure 1 above, the specimen (A) migrates via capillary action along the membrane to react with the colored conjugate (B). COVID-19 antibody present in the specimen bind to the conjugate, forming a colored antibody-antigen complex (C). COVID-19 antibody immobilized in the test line region of the membrane captures the complex. The formation of a visible red line indicates a positive result (D). The absence of a red line formation in the test line region indicates a negative result. In the control line region of the membrane, immobilized reagents capture colored conjugate regardless of the test specimen composition. The resulting visible red line (E) confirms that the assay is functioning correctly.
How accurate are Covid-19 antigen rapid tests?
PCR | COVID-19 Antigen Rapid Test Device | ||
Positive | Negative | TOTAL | |
Positive | 145 | 5 | 150 |
Negative | 0 | 487 | 487 |
TOTAL | 145 | 492 | 637 |
Relative Sensitivity: 145/150 96.67% (95%CI:92.39%~98.91%) Relative Specificity: 487/487 100% (95%CI:99.39%~100%) Overall Agreement: 632/637 99.22% (95%CI:98.18%~99.74%) | |||
Table: COVID-19 Antigen Rapid Test Device vs. Real-Time PCR
Sensitivity
COVID-19 Antigen Rapid Test Device has an overall sensitivity of roughly 96.67 percent, which means that they are catching roughly 96 percent of people who are infected with the virus and missing only 4 percent.
Specificity
A false positive is when you test positive for COVID-19 when you don’t actually have it. COVID-19 Antigen Rapid Test Device rarely gives a false-positive result.
Why COVID-19 rapid tests are used?
Despite the relatively high chance of getting a false negative result, COVID-19 rapid tests offer several benefits over PCR tests.
Rapid tests:
●can provide results within 15 minutes instead of days
● are more portable and accessible than PCR tests
●are less expensive than PCR tests
●don’t require a lab or special lab equipments