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Are Rapid Covid-19 Test Results Reliable?

by Gauri Kolhe

In today’s chaotic scenario where millions of the people are suffering from covid-19 worldwide, it is really necessary to know about the rapid covid-19 test.

So covid-19 is respiratory disease and associated with the inflammation in the respiratory tract and severe illness with the risk of high mortality rate.

It is quite risky in people who already have pre-existing medical conditions like obesity, high blood pressure, cardiac disorders and diabetes.

Basically covid-19 causes by the infection due to virus SARS-CoV-2. Covid-19 can be detected by two tests which are PCR and antigen test.

First test which sis PCR, polymerase chain reaction also known as diagnostic test and molecular tests.

Generally PCR techniques is used b many scientists to make billions of the copy of DNA but this also helps in detecting covid-19 as PCR  detects genetic material of the corona virus. Centres for disease control and prevention (CDC) considered PCR as a gold standard.

Generally antigen test detects the presence or absence of antigen and results are visible to naked eyes. Second test is antigen test which helps in detection of covid-19 by detecting certain specific molecules on the surface of SARS-CoV-2 virus.  

For detection of covid-19 rapid test are used and they takes hardly 5 to 30 minutes to show the result. Apart from this they don’t have a need of laboratory analysis. Usually rapid test is antigen tests.

Even though rapid test is quite known for providing quick results, rapid test are not accurate as compared to PCR tests.

So it is necessary to know that how reliable rapid covid-19 tests are?

Accuracy of rapid covid-19 test:

Rapid covid-19 test do not require to be analyze in laboratories, they provide rapid results within 30 minutes. Most of the rapid tests are antigen test or considered as vice-versa.

The CDC recommends to stop using “rapid” in order to describe the antigen tests. The term rapid test also can be called as point-of-care tests and they can easily performed at various places such as:

  • Doctor’s office
  • Pharmacies
  • School clinics
  • Home  
  • long term care facilities
  • airports
  • drive through testing sites

In this test a medical professional even you can do it on yourself, a cotton swab will insert into the nose, throat  or sometime both to collect the sample which is mucus and cells. After that this sample place to the strip.

The colour change of the strip indicates that you are covid-19 positive. Even though these tests are quick and give result within 30 minutes, they are not accurate like tests performed in the laboratory as rapid tests require a higher amount of virus in your sample to be detected.

Rapid tests have the high risk of giving a false negative result even though you have positive with covid-19 sometimes.

In other words in actual you are coivd-19 positive but rapid tests show you the covid-19 negative hence the result calls as false negative and they are not reliable.  

Possibilities of a rapid test giving false negative:

In march 2021 review of studies surveyed test accuracy of rapid test by evaluating results of 64 test accuracy studies. As a result researchers found that the accuracy of the rapid test depends on various factors and here are some of the findings mentioned below:

accuracy for the people having the symptoms of covid-19:

Rapid tests gave a correct positive test for the people who have the symptoms of covid-19. The positive average result was 72 % of the time.

The results of the study lied between the range of 63.7 to 79 percentage, in other words researchers were 95 % sure about the results.  

accuracy for the people  do not having symptoms of covid-19

Researchers found people do not having symptoms of covid-19 tested positive in for 58.1 percentage of rapid test. They have 95 % confidence that results lied between the ranges of 40.2 to 74.1 percentages.

accuracy during the first  between  second week of the symptoms

Finding of accuracy also varied in rapid test when they are done in first eek and second week of the symptoms. in a study researchers found that rapid tests provide accurate result when operated during the first week of having the symptoms.

An average of 78.3 % of cases during first week was identified correctly by rapid tests. While in the second week the average of accuracy dropped to the 51 percentage.

accuracy on difference between the brands

As there rapid tests of different brands are available in the market, the accuracy of the result varied in a large range between the various manufacturers.

Coris bioconcept’s rapid test kit get the minimal accuracy by providing poorest and correctly positive covid-19 result only 34.1 percentage of total cases.

On other hand SD Biosensor STANDARD Q scored the highest result and correctly identifies the positive covid-19 result in 88.1 percentages of the total cases.

A study was published in April 2021 which shows the comparison of the accuracy of the four types of the rapid covid-19 tests.

In this study researchers found that all tests correctly identified a covid-19 positive case for about the half of the time and almost all the time they correctly identified the covid-19 negative cases.

Rapid test of the ROCHE get a score of 49.4% in positive case and 100 % in detection of negative cases.

ABBOT get a score of 44.6% and 100% covid-19 positive and negative respectively.

MEDsan get an accuracy of 45.8% in detection of positive while 97% in the detection of coivd-19 negative cases.

Siemens identifies the highest of 54.9 % accurately the covid-19 positive cases while successful in detection of 100% of covid-19 negative cases.

Although rapid tests are less accurate, they are used widely why?

Even after have a high chance of getting a false negative results, rapid covid-19 tests provide some benefits over the laboratory tests such as PCR. Here are some benefits of rapid tests are mentioned:

As the name indicates they give result within minutes instead of the days

Rapid tests are more accessible and easily portable than laboratory tests

In terms of expense rapid covid-19 tests are less expensive than laboratory test

And the most importantly those rapid covid-19 tests do not require specialist or a laboratory. Most of the public places like airports, theme parks, arenas, markets or many other areas offer rapid tests for the vcovid-19 screening of potential positive cases.

Even rapid tests won’t correctly detects every covid-19 case but they case detect at least some cases of covid-19 that.

If you have symptoms of covid-19 but get a negative result then what should you do?

If you experiencing symptoms of covid-19 and gone through a rapid test but get a negative result then you should go for the PCR test to get more accurate and confirm result.

When it comes to the accuracy how accurate are other tests is also a matter of concern. So how accurate are other covid-19 test are?

PCR test:

As PCR is sophisticated test, it holds the gold standard for the diagnosis of covid-19. In a study published in January 2021 it was found that PCR test for the mucus diagnosed covid-19 in 97.2 percentages of cases.

Computed tomography (CT) scans

Generally Computed tomography is used in the diagnosis of many diseases. CT scan is not an official test associated with structures of virus or other molecular study but CT Scans can potentially identify the COVID-19 by detecting problems in lungs due to covid-19 infections.

Although they are less practical and hard to notify the Cocid-19, they are used in hospitals.

Antibody tests:

In antibody tests detection of proteins has done which are produced by you immune system called as antibody. In case of corona these test detects for the antibodies IgM and IgG. Antibody test cannot detect covid-19 infection.

But in a study published in January it was found that presence of IgM and IgG detected in antibody test by 84.5% and 91.6 % respectively.

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