A lateral flow test (LFT) is a type of Covid-19 diagnostic test used to detect certain antibodies in saliva or other body fluids. It is a quick and easy way to determine if an individual is infected with the virus. But what makes an LFT positive?

This article explores the answer to that question. We’ll look at what constitutes a false positive, how to take the lateral flow test properly, and everything else you need to know about LFT.

Testing for Covid-19

Testing for Covid-19 has become an integral part of our lives. Apart from lateral flow tests, several other testing methods are used to detect the virus. They include the following:

Rapid Antigen Test

A rapid antigen test quickly detects fragments of proteins that are found on the surface of the virus. It is one of the most commonly used tests and yields results within 15 minutes.

How is an antigen test done? First, a sample of secretions such as saliva or nasal swab is collected from the patient. The sample is then applied to a device that contains antibodies specific to the virus. If it detects any proteins on the surface of the virus, then it will bind with those proteins and show a positive result.

One of the questions most people ask is: Is a rapid test an antigen test? The simple answer is yes. A rapid antigen test is indeed one of the COVID-19 antigen tests, but it is much faster and more accurate than other antigen tests.

What does a rapid antigen test do? A rapid antigen test simply identifies the presence of antigens from a particular infectious organism. This helps doctors quickly diagnose an infection and take appropriate action.

POC Antibody Test

A POC (Point of Care) antibody test detects antibodies against the virus in a patient’s blood or saliva sample. It can be done either by lateral flow assay or ELISA (enzyme-linked immunosorbent assay). It works by detecting the presence of antibodies in a patient’s sample, which can be indicative of an active infection.

RT-PCR (Reverse Transcription Polymerase Chain Reaction)

RT-PCR is a highly sensitive and accurate test that is used to detect the presence of viral genetic material. It involves extracting genetic material from a patient’s sample and then amplifying it using PCR (Polymerase Chain Reaction). This amplified material can then be detected using special laboratory equipment.

What Makes False Positives?

COVID-19 lateral flow tests are known to be more accurate than most COVID-19 antigen tests. However, false-positive test lines may still occur. A false-positive is an incorrect result that indicates a person has the disease even though they don’t.

The most common cause of false positives on COVID-19 lateral flow tests is cross-reactivity. Cross-reactivity occurs when antibodies to other diseases bind to antigens in the test and trigger a false positive result. Cross-reactivity can occur with lateral flow tests due to the lower sensitivity of these tests.

It’s also possible for a false positive to be caused by human error or contamination of the sample, such as when someone doesn’t follow proper testing procedures. Contamination can occur if the person administering the test has not adequately cleaned their hands or equipment.

How to Take the Covid-19 Lateral Flow Test Properly?

There are several important steps to follow to prevent false positives when taking a lateral flow test. They include:

Collect Samples Correctly

The person administering the test should ensure that enough sample is collected onto the swab or specimen collection device. A good amount of mucosal secretions from the posterior pharynx and nasal cavity are necessary for accurate results.

Label Specimens Properly

Another important step is to label specimens correctly. It is important to clearly document the name of the person being tested, the date and time when the specimen was taken, and any additional information that may help identify the test result as belonging to a particular individual.

Check Directions Carefully

It is also essential that all directions are read thoroughly before administering the test. The operator should ensure that all steps are followed as indicated in the package instructions and that the proper technique is used.

Sensitivity of the Test

The sensitivity of lateral flow tests depends on whether the patient is symptomatic or asymptomatic. Asymptomatic people tend to have a lower level of the virus in their system, making them harder to detect. This means that for asymptomatic people, the sensitivity of the test should typically be higher than it is for symptomatic patients. In general, lateral flow tests are more sensitive than RT-PCR tests and can detect smaller amounts of the virus present in the body.

Final Thoughts

Now that you know the basics of how to take a lateral flow test properly and what factors affect its accuracy, you can use this information to make sure that your results are accurate. Remember, if there is any doubt about the accuracy of the results, it doesn’t hurt to take the test again. Doing so will help ensure that you are getting accurate, reliable results. Good luck!