How Accurate Is Rapid HIV Test?

The rapid HIV test is an assay that is intended to identify HIV antibodies or antigens in a patient’s blood or oral secretion. It delivers results in 20-30 minutes, and thus, it can be considered a rapid method that allows persons to get HIV status quickly. The test is easily accessible in clinics, community centers, and through home-testing kits, which has made it popular. In this article, we will discuss the different factors that can influence the reliability of rapid HIV testing, how the test is done, and what clients can anticipate on their HIV test results.  

Understanding How the Rapid HIV Test Works

For one to comprehend the functionality of the Rapid HIV Test they have to comprehend the following: As a matter of accuracy, it is necessary to know how the rapid HIV test works, first of all. Most  rapid HIV tests work by detecting either: 

• HIV antibodies: These are proteins that are made by the body in reaction to the existence of HIV in the body. Antibodies generally develop between two and twelve weeks after the infection has occurred. 
• HIV antigens: Especially, p24 antigen which is a protein of the virus and can be detected earlier than antibodies, at the time 2-4 weeks after the onset of the infection. 

Rapid HIV tests are of various forms and they include oral swabs, finger stick blood tests as well as the home HIV testing kits. If the test picks these markers, it will be positive implying that the person being tested might have HIV infection. 

Accuracy of Rapid HIV Tests

When discussing accuracy, two terms are important: sensitivity and specificity. 

• Specificity is the extent to which the rapid test is accurate in determining those who are negative for HIV. High sensitivity in a test means there will be fewer instances of false negatives, that is when the test will return negative when the person has HIV. 
• Sensitivity, on the other hand, is the capacity of the test to correctly identify non-HIV-negative people. Specificity indicates that there will be fewer samples that will be identified as positive while the actual person being tested is HIV-negative. 

Sensitivity and Specificity of Rapid HIV Tests 

Rapid HIV tests are very sensitive and specific because they are intended to produce results within 20 minutes. Currently, most rapid tests in the market have a sensitivity rate of above 99% which indicates that they are very efficient in the detection of HIV in infected persons. They also have a specificity rate that is over 99% meaning that chances of getting a false positive result are minimal.  

Why are False Negatives Possible? 

What should be borne in mind is that, though the accuracy rates of rapid HIV tests are as high as 99%, they are not entirely accurate at any time and there is the so-called ‘window period’. The window period is the time between the period one has contracted HIV and the time the test can reveal the virus. For the rapid test, this period is between two and twelve weeks depending on whether the test is done by antibodies or antigen. 

A problem that may be observed is the false negative result, which is likely to be observed in case the individual takes the test before the target biomarkers such as antibodies or antigens, are produced within the body. That is why, health care providers suggest repeating the test after the window period or using more effective methods such as the fourth-generation HIV test that is capable of detecting both HIV antibodies and antigens at an earlier stage than the third-generation HIV test. 

Why True Negatives Are Possible? 

It is however important to note that while the false positive results are infrequent, they are caused by the specificity rate of the test. A false positive may be a result of the test detecting some substance in the blood or oral fluid as HIV-related antibodies or antigens. This can occur if the test responds to other infections or states, although this is rare. 

The next thing that one is supposed to do, in case of a positive rapid HIV test, is to take a confirmatory test such as the Western blot test or the HIV RNA test to ensure that the result is not a false positive. 

Factors That Influence the Accuracy of Rapid HIV Tests

Several factors can affect the accuracy of a rapid HIV test, including:

• Timing of the Test: As mentioned earlier, the taking of the test during the window period is likely to produce some inaccurate results. It is very possible to get a negative result if the test is administered immediately after getting infected with the virus. 
• Test Quality: It is therefore important to understand that the quality of the test that is being conducted has a great influence on the accuracy of the results obtained. Labs authorized by the FDA are highly credible, and the tests are highly accurate; however, not all the tests in the market may be as credible. 
• User Error: Self-administered HIV testing kits can be affected by errors by the users of the kits. If the laid down instructions are not followed properly then it may result in the wrong outcome. This is why it is recommended that any person who is in doubt about how to go about the process should follow the provided instructions in the letter. 
• Type of Sample: There are blood-based rapid HIV tests and there are oral fluid-based rapid HIV tests as well. Blood-based tests are further preferred than oral fluid tests because, in comparison, blood contains higher HIV antibodies than oral fluid. 
• Test Conditions: Some of the test conditions that can influence the result of the test include temperature and humidity among others. By improper storage or usage in other conditions that are not favorable for the test, the result may be affected.

Conclusion 

HIV rapid tests are one of the most effective ways of fighting HIV because they enable people to know their status within a short period. As the sensitivity and specificity rates show, the accuracy of these tests is quite high, nevertheless, there are certain drawbacks. The window period, test quality, and user error are some of the factors that can lead to the results. People should get a second test to confirm the results if they get a positive result; people should also be aware of the window period when testing for HIV.  

FAQ’s

Q1: How soon after exposure can a rapid HIV test detect the virus? 

The rapid HIV test can identify HIV antibodies or antigens within 2 to 12 weeks after exposure. During this period, testing is important to obtain accurate results, but if the exposure was recent, then a second test is advised.  

Q2: Can a rapid HIV test result be negative? 

Indeed, the test is negative if it is taken within the window period before the body starts producing detectable levels of antibodies and antigens. The window period is advised to be retested to confirm the HIV status.  

Q3: Does one get a confirmatory test after a positive rapid HIV test?  

Indeed, a follow-up test is required after the rapid HIV test has produced a positive result. To exclude the possibility of a false positive result, additional tests such as the Western blot or HIV RNA test are employed.

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