What is the Difference Between Rapid Test and Swab Test

Rapid test and swab test are two diagnostic tests used to diagnose severe viral infections, including the COVID-19 infection. Sometimes, both these tests are performed simultaneously for the accurate diagnosis of the causative agent of the diseases.

The key difference between rapid test and swab test is their mechanism of action. Rapid test is a diagnostic test that detects antibodies or antigens in the body using a blood sample, while swab test is a diagnostic test that uses a swab to take a small sample of cells from the nose and throat, which is then tested through laboratory culturing.

CONTENTS

1. Overview and Key Difference
2. What is a Rapid Test  
3. What is a Swab Test
4. Similarities – Rapid Test and Swab Test
5. Rapid Test vs Swab Test in Tabular Form
6. Summary – Rapid Test and Swab Test
7. FAQ – Rapid Test and Swab Test

What is a Rapid Test?

Rapid test is a method of checking the test results quickly and accurately. Rapid test usually uses a cartridge device to determine the presence of antibodies in the body from blood samples when there is a viral infection. Moreover, some rapid tests are developed based on the detection of antigens rather than antibodies, such as rapid antigen tests. For SARS-COV2, a rapid test is performed to screen patients under surveillance (PDP) and people under surveillance (ODP).

Figure 01: Rapid Test

For this test, the blood sample is taken from a capillary (finger) or from a vein. Rapid tests cannot detect antibodies the first-time people are sick. This is because antibodies may not be formed at this stage or antibody levels may be still low. Therefore, if this test results are non-reactive, the test must be repeated 7-14 days later to confirm whether the person has the infection.

What is Swab Test?

In swab test, a swab of throat or nose is used to detect an infection. Once the sample is collected, it will be sent to the lab for culturing. This test procedure involves collecting a sample from the site of infection and inoculating the sample into solid or liquid nutrient media (e.g., agar, gelatin) in order to grow any microorganisms like bacteria or virus for the detection.

Figure 02: Swab Test

After incubation of culture plates, the laboratory professional will visually examine the culture and detect samples based on the characteristics of the microorganism. The culture results will be recorded in the laboratory information system, and the results may be sent to the health practitioner electronically. The problems with the swab test are that it needs trained professionals and it is time-consuming.

Similarities Between Rapid Test and Swab Test

1. Rapid test and swab test are two diagnostic tests.
2. Sometimes, both these tests are performed simultaneously for the accurate diagnosis of the causative agent of the diseases.
3. They can be used for the detection of viral infections such as COVID-19.
4. Both these tests have advantages as well as disadvantages.

Difference Between Rapid Test and Swab Test

Definition

• A rapid test is a test that detects microorganisms either by identifying antibodies against the microorganism or antigen of the microorganism by using a blood sample.
• A swab test is a test that detects microorganisms by laboratory culture characteristics of the microorganism by using a nasal or throat swab.

Time

• A rapid test takes 5 to 30 minutes.
• A swab test takes 2 to 3 days.

Need of Trained Professionals

• There is no need of trained professionals in a rapid test.
• A swab test needs trained professionals.

Benefits

• Benefits of rapid tests are quick, require minimal training and infrastructure (point of testing), and cost advantages.
• A swab test needs a minimal cost.

Problems

• Non-reactiveness, in some instances, is a problem with rapid tests.
• Swab tests need infrastructure facilities and time-consuming.

Examples

• One example is the rapid antigen test for COVID-19.
• Swab test for COVID-19, flu, whooping cough, meningitis, respiratory syncytial virus (RSV) and methicillin resistant Staphylococcus aureus (MRSA) are some examples.

The following table summarizes the difference between rapid test and swab test.

Summary – Rapid Test vs Swab Test

Rapid test and swab test are two diagnostic tests that detect viral infections such as COVID-19. Rapid test identifies the infectious microorganism by detecting antibodies against microorganism or antigens of the microorganism in the blood of the body. Swab test identifies the infectious microorganism by detecting the characteristics of the microorganism through culturing a swab sample in the laboratory. This is the basic difference between rapid test and swab test.

FAQ: Rapid Test and Swab Test

1. What can rapid test detect?

• Rapid test detects antigens of the microorganism or antibodies against microorganism in the blood samples of the patient. In a rapid test, a negative test doesn’t necessarily mean the patient doesn’t have the infection.

2. Why is rapid test important?

• Rapid tests are important because they help manage diseases better. They quickly confirm infections, which means doctors can use the right medicines more effectively to treat the infection. Rapid tests also give clear instructions on what to do, whether the result is positive or negative.

3. How to collect a swab sample?

• A 1.5 cm inch swab is inserted into the nose or throat without touching the soft end with the hands. In the case of nasal swabbing, gently press against the inside of the nostril at least 4 times for a total of 15 seconds. Collect as much nasal discharge as possible on the soft end of the swab.

4. Can a swab test detect viruses?

• Yes. Nose swabs are commonly taken from patients who are suspected of having respiratory infections. These swabs are tested to detect specific signatures of 10 to 15 known viruses such as SARS-CoV-2, RSV, influenza, etc.

5. How long do swab test results take?

• It takes between 48-72 hours for the laboratory to process the results. If the swab test comes back with a positive result, laboratory-trained professionals will inform the GP either by phone or by letter.

Reference:

1. “Nasal Swab: Medical Test.” MedlinePlus, U.S. National Library of Medicine.
2. “Legionella Test Kits Supplier – Instant STI Test Manufacture.” Hysen Biotech.

Image Courtesy:

1. “Close-up of a Rapid Antigen Test Kit” (CC0) via Pexels
2. “A Woman Getting a Swab Test” (CC0) via Pexels

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