TESTING

FOR

HIV AND AIDS

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[TE6]

HOW DO DOCTORS TEST FOR HIV?

The most common way to diagnose HIV is through blood tests. With the blood samples, doctors can conduct different types of tests:

Enzyme-Linked Immunosorbent Assay (ELISA)
- This test detects HIV antibodies and antigens. The blood is put into a specific cassette and if HIV antibodies are present, they will bind to the antigen and cause the cassette to change colors. [TE1] A journey of biological discovery
Viral Load Tests
- These tests measure the amount of the virus in the blood by using specific DNA sequences that bind with HIV. Doctors use 3 different methods to do so:
  - Reverse Transcription Polymerase Chain Reaction (RT-PCR)
  - Nucleic Acid Sequenced Based Amplification Assay (NASBA)
  - Branched DNA (bDNA) [TE2]

There are other ways to diagnose HIV without the use of blood samples, however, they are usually followed by blood tests to confirm any positive results:

Saliva Tests
Home Tests
- The only one approved for use in the United States is the Home Access Express Test. [TE3]

ELISA

TEST

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VIRAL LOAD

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SALIVA

TEST

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HOME

TEST

[TE10]

HOVER OVER ME

THE ELISA TEST

The ELISA test is a commonly used HIV detection

test.

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Some important terms that need to be clarified in order to understand how the ELISA test works include:

Antigen: a substance from a bacteria or virus that cause the immune system to react if it gets inside the body
- p24 Antigen: a viral protein that makes up the HIV core and is easily detectable in early screening tests
Antibody: a Y-shaped immune cell that attaches to antigens and prevents it from causing harm [TE4]

ELISA HIV TEST: THE PROCESS

Antibodies for the p24 antigen are placed inside either a petri dish or a well plate. [TE5]

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The sample is washed with a second antibody that is specific to humans. This 2nd antibody has a marker attached to the end of it (the yellow dot). [TE5]

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S

T

E

P

O

N

E

S

T

E

P

T

W

O

Blood is added to the container and 2 things can happen:

The p24 antigen will attach to the antibodies = HIV POSITIVE
Nothing will attach to the antibodies because there are no antigens = HIV NEGATIVE [TE5]

S

T

E

P

T

HREE

Then another antibody that is specific to the p24 antigen is added on top of everything else.

If it attaches, the antigen is present.
If not, the antibody washes away. [TE5]

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S

T

E

P

FOUR

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T

E

P

F

I

VE

Lastly, a dye is placed inside of the container that will change colors if the 2nd antibody markers are present.

Colored= HIV POSITIVE
Clear= HIV NEGATIVE [TE5]

HIV AND AIDS

A JOURNEY OF BIOLOGICAL DISCOVERY

[HF1]

[HF1]

TESTING

FOR

HIV AND AIDS

​

[TE6]

HOW DO DOCTORS TEST FOR HIV?

The most common way to diagnose HIV is through blood tests. With the blood samples, doctors can conduct different types of tests:

Enzyme-Linked Immunosorbent Assay (ELISA)

This test detects HIV antibodies and antigens. The blood is put into a specific cassette and if HIV antibodies are present, they will bind to the antigen and cause the cassette to change colors. [TE1] A journey of biological discovery

Viral Load Tests

These tests measure the amount of the virus in the blood by using specific DNA sequences that bind with HIV. Doctors use 3 different methods to do so:

Reverse Transcription Polymerase Chain Reaction (RT-PCR)

Nucleic Acid Sequenced Based Amplification Assay (NASBA)

Branched DNA (bDNA) [TE2]

There are other ways to diagnose HIV without the use of blood samples, however, they are usually followed by blood tests to confirm any positive results:

Saliva Tests

Home Tests

The only one approved for use in the United States is the Home Access Express Test. [TE3]

ELISA

TEST

[TE7]

VIRAL LOAD

[TE8]

SALIVA

TEST

[TE9]

HOME

TEST

[TE10]

HOVER OVER ME

THE ELISA TEST

The ELISA test is a commonly used HIV detection

test.

[TE11]

Some important terms that need to be clarified in order to understand how the ELISA test works include:

Antigen: a substance from a bacteria or virus that cause the immune system to react if it gets inside the body

p24 Antigen: a viral protein that makes up the HIV core and is easily detectable in early screening tests

Antibody: a Y-shaped immune cell that attaches to antigens and prevents it from causing harm [TE4]

ELISA HIV TEST: THE PROCESS

Antibodies for the p24 antigen are placed inside either a petri dish or a well plate. [TE5]

[TE12]

The sample is washed with a second antibody that is specific to humans. This 2nd antibody has a marker attached to the end of it (the yellow dot). [TE5]

[TE12]

[TE12]

[TE12]

S

T

E

P

​

O

N

E

S

T

E

P

​

T

W

O

Blood is added to the container and 2 things can happen:

The p24 antigen will attach to the antibodies = HIV POSITIVE

Nothing will attach to the antibodies because there are no antigens = HIV NEGATIVE [TE5]

S

T

E

P

​

T

HREE

Then another antibody that is specific to the p24 antigen is added on top of everything else.

If it attaches, the antigen is present.

If not, the antibody washes away. [TE5]

[TE12]

S