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Introduction of HIV, HBsAg, and HCV Tests 

HIV, HBsAg, and HCV tests are positive as shown above image. These HIV, HBsAg, and HCV rapid tests or screening or quick tests are applicable for the diagnosis of Human Immunodeficiency Virus (HIV), Hepatitis B (HBV), and Hepatitis C (HCV) infections. They all are serological tests and carried out on blood samples obtained by venous puncture.

HIV Rapid Test

The diagnosis of HIV infection is usually based on the detection of antibodies to HIV in AIDS patients.  Development detectable antibodies mostly occur within 3 months after infection. But the average is being 25 days whereas in rare cases, it can take up to 6 months.

Who is more prone to HIV?

Are you a man who has had sex with another man?
Have you had sex—anal or vaginal—with an HIV-positive partner?
Have you had more than one sex partner?
Have you injected drugs and shared needles or works (for example, water or cotton) with others?
Have you exchanged sex for drugs or money?
Have you been diagnosed with, or sought treatment for, another sexually transmitted disease?
Have you been diagnosed with or treated for hepatitis or tuberculosis (TB)?
Have you had sex with someone who could answer “yes” to any of the above questions or someone whose sexual history you don’t know?
Sexually active gay and bisexual men may benefit from more frequent testing (for example, every 3 to 6 months).

HBV Test 

The diagnosis of HBV infection is generally made on the basis of serological markers detected by ELISA assay. Serologic markers of HBV infection vary depending on whether the infection is acute or chronic.

In acute HBV infections, hepatitis B surface antigen (HBsAg) is the first serologic marker to appear in the blood. It can be detected as early as 1 or 2 weeks and as late as 11 or 12 weeks after infection by HBV. In persons who recover, HBsAg is no longer detectable in serum after an average period of about 3 months.

Different biomarkers of HBV are as follows :

• HbsAg
• Anti-HBc IgM
• Anti-HBc IgG
• Anti-HBs
• HBV DNA
• HBeAg
• Anti-HBe

HCV Test

Testing for the presence of HCV antibodies is recommended for initially identifying persons with hepatitis C virus infection. Testing for HCV antibodies should include use of an antibody-screening assay and, for positive results of this screening test, a more specific additional assay  Hepatitis C (HCV) is a viral infection of the liver, which had been referred to as parenterally transmitted “non-A, non-B hepatitis” until the identification of the causative agent, in 1989. HCV is a major cause of acute hepatitis and chronic liver disease, including cirrhosis and liver cancer. Worldwide, unscreened blood transfusions and re-use of needles and syringes that have not been adequately sterilized are the major causes of HCV infection. Studies on HCV risk factors indicate that the vast majority of prevalent HCV infections are through injecting drug use.
In injecting drugs users (IDUs), the prevalence rate of HCV ranged from 50 to 80%

Principle of HIV, HBsAg, and HCV Tests

These tests work on the principle of immunochromatography and thus let’s know in detail. The immunochromatographic test principle is the same as the sandwich ELISA method. The only difference is that immunological reaction is carried out on the chromatographic paper by capillary action. For this system, two kinds of specific antibodies against the antigen are used. One of the antibodies is immobilized on the chromatographic paper while another is labeled with colloidal gold and infiltrated into a sample pad. An immunochromatographic unit is completed by attaching the sample pad at the end of the membrane. The liquid sample is dropped on the sample pad. The antigen in the sample forms an immunocomplex with the antibody labeled with colloidal gold. Its complex moves along with the liquid sample and makes a contact with the antibody immobilized on the membrane. It is followed by forming an immuno- complex with the immobilized antibody. It results in generating a colored red-purple line.  The appearance of a red-purple line on the membrane indicates the presence of antigen of interest in the sample. The liquid of the sample migrates through the membrane very fast, it makes it possible to detect the presence or absence of antigen within 15 minutes as shown above image.

Components of Immunochromatographic Test Device

Sample pad: It acts as a sponge and holds an excess of sample fluid. Once soaked, the fluid migrates to the second element.
Conjugate pad: A dried format of bio-active particles in a salt-sugar matrix that contains everything to guarantee an optimized chemical reaction between the target molecule (e.g. an antigen) and its chemical partner (e.g., antibody) that has been immobilized on the particle’s surface.

Control: It contains an antibody that picks up free latex/gold in order to confirm the test has operated correctly.

Test: It contains a specific capture molecule and only captures those particles onto which an analyte (antigen or antibody ) molecule has been immobilized.

Procedure of HIV, HBsAg, and HCV Tests

Take an alcohol swab and disinfect the site of the prick. Take a pricker and puncture the area below the fingertip. Ooze the blood. In case of where there is a need for serum or plasma, follow this procedure of blood collection. Clean venipuncture site with chlorhexidine or povidone-iodine using back and forth friction scrub for 30 seconds. Allow it to dry for 30 seconds. Do not retouch the site; if you must repalpate for vein, the area must be re-cleaned using the above procedure. Perform venipuncture. When the required amount of blood is received, remove the needle from the skin. Hold pressure to site with gauze and apply adhesive bandage when the bleeding stops. Inject blood specimens into a red-protected vial for serum or EDTA purple vial for plasma. After clotting the blood, centrifuge the vial in case of serum but no waiting for clotting in case of plasma separation. Discard needle and syringe into a sharp container. Take two drops (the volume depends on the nature of test and manufacturer guidelines) with sucker and dispensed in sample hole of the strip. Add buffer to sample. Wait for 10-15 minutes. Observe results and interpret accordingly.

Note: For those immunochromatographic tests in which whole blood is applicable e.g. Malaria rapid diagnostic test in the diagnosis of Malaria for detection of Plasmodium species (vivax or falciparum) antigens.

Result Interpretation of Immunochromatographic Test

Test negative: Only on the band at the control region

Test positive: Both bands at test and control regions

Test invalid: No band at all or band only at the test region

Note: HIV, HBsAg, and HCV tests are positive as shown above image because of having both bands at the control and test regions or lines.

Uses of HIV, HBsAg, and HCV Tests

The application of these tests are very helpful for the following purposes-

1. Access to appropriately resourced services for people at risk of acquiring infection and for those diagnosed with  infection to optimize monitoring and clinical management, and to ensure timely referral to treatment
2. The reduction of  transmission through knowledge of one’s status;
3. The reduction of transmission from a mother with infection to her newborn;
4. Monitoring the response to vaccination ( e.g. against HBV) at an individual and community level;
5. Documenting the epidemic to aid the development of evidence-based public health interventions
6. The improvement of the health of people who have chronic infection.

Advantages of HIV, HBsAg, and HCV Rapid Tests

• Improvement of clients’ satisfaction who can rapidly receive their results
•  Easier and safer to use
• Enhancement of the autonomy of people to be tested since they will be able to choose between conventional testing and rapid testing,
• More people would receive their results (only one medical counseling)

Bibliography

1. https://www.wiv-isp.be/epidemio/epien/birn/biotest.pdf
2. https://www.hiv.gov/hiv-basics/hiv-testing/learn-about-hiv-testing/hiv-testing-overview
3. https://www.cdc.gov/hiv/basics/testing.html
4. http://testingportal.ashm.org.au/hbv/introduction
5. https://www.creative-diagnostics.com/Immunochromatography-guide.htm