CHAPTER 2: HIV TESTING TECHNOLOGIES

The Ethiopian Public Ministry of Health-Ethiopia

2
Health Institute
 Enabling objectives
At the end of this section participants will be able to.

• Explain the Spectrum of HIV testing Technologies

• Identify complexity of HIV Testing technologies

The Ethiopian Public Ministry of Health-Ethiopia

3
Health Institute
 Outlines:
 Spectrum of HIV Testing Technologies

 Complexity of HIV Tests

 Chapter Summary

The Ethiopian Public Ministry of Health-Ethiopia

4
Health Institute
 Spectrum of HIV testing
• .

Technologies
Activity 2.1. Self-Reflection
Instruction: Reflect your ideas on the following
questions

List the current HIV testing technologies

Time: 5 minutes

The Ethiopian Public Ministry of Health-Ethiopia

5
Health Institute
 Spectrum cont.….
 The period immediately following HIV infection is the

eclipse period.

 During eclipse period no assay can detect HIV as;

The amount of nucleic acid from the virus is miniscule

 Low amount of antibodies are produced only in

response to the presence of the virus

The Ethiopian Public Ministry of Health-Ethiopia
6
Health Institute
 Spectrum cont.….
 HIV testing technologies categorized as serological and

Virological assays.

 Virological assays can detect as early as 12 days of HIV

infection.

 Whereas serological assays need nearly 18 days to detect the

concentrations of antibodies in the body fluid.

The Ethiopian Public Ministry of Health-Ethiopia
7
Health Institute
 Spectrum cont.….
.

The Ethiopian Public Ministry of Health-Ethiopia

8
Health Institute
 Spectrum cont.….
 The length of HIV detection period affected by
 The type of serological assay used,
An individual’s immune response,
The type of the body fluid used.

 Based on the composition of the antigen and what the assay

detects serological assays categorized in to four
generations .
 Fourth generation assays that detect both HIV p24 Ag and
Ab can potentially identify HIV-infected
The Ethiopian Public
Health Institute
9
individuals during
Ministry of Health-Ethiopia
 Spectrum cont.….
.

The Ethiopian Public Ministry of Health-Ethiopia

10
Health Institute
 Spectrum cont.….
• Serological Assays
Activity 2.2. Think/Pair/share
Instruction: First take a while to think on the
following questions and be in pair with a partner
seating next to you and share your idea regarding
the question and reflect what you have discussed
to the larger group.
1.1.1. What are the three Phenomenon’s on the
serological reaction?
Time: 4 min to think and share to your partner and
1 minute for reflection

The Ethiopian Public Ministry of Health-Ethiopia

11
Health Institute
 Serological Assays
 There are three Phenomenon's on Antigen-antibody
reactions
Pro zone phenomenon- false negative resulting from excess
antibody titer which interferes with formation of Antigen-
antibody lattice
Post zone phenomenon- is false negative resulting from
excess antigen titer
Equivalence zone – proportional amount of antibody and
The Ethiopian Public Ministry of Health-Ethiopia
12
Health Institute
 Rapid Diagnostic Test:
 HIV rapid tests are qualitative assays that detect HIV
antibodies.
 Most of them can detect HIV-1 and HIV-2 and they are as
reliable as EIAs.
 There are three main formats or types of rapid HIV tests

 Immuno-concentration (flow-through device

 Immuno-chromatography (lateral flow)

 Particle agglutination
The Ethiopian Public Ministry of Health-Ethiopia
13
Health Institute
 Immuno-concentration (flow-through
device)
 Immuno-concentration  Presence of HIV Ab is
devices are usually indicated by colored spot or
cartridges with HIV antigen line.
attached to a membrane.
 The specimen and individual
reagents are each added to
the cartridge in a series of
steps.
The Ethiopian Public Ministry of Health-Ethiopia
14
Health Institute
 Immuno- chromatography
 Specimen is applied to a pad  If HIV Ab are present, a red line
(filter) where it mixes with gold will form in the test area of the
Add
or selenium colloid- antigen strip
Sample
Test
Control
Conjugate
conjugate. Line
Line

 This mix migrates through the

nitrocellulose strip to
immobilized recombinant
antigens and synthetic peptides
at the patient window. .
Eg One step anti-HIV (1&2), First response
HIV-1, Uni-Gold HIV, Stat pack

The Ethiopian Public Ministry of Health-Ethiopia

15
Health Institute
 Particle agglutination
 Agglutination assays were
among the first of the rapid tests
developed.

 The round circles represent

antigen-coated latex particles
that bind to antibodies to HIV
(represented by the “Y”).

 Agglutination or clumping occurs

when the antibodies bind to the Eg, Capilus
antigen-coated particles.
The Ethiopian Public
Health Institute
16
Ministry of Health-Ethiopia
 HIV Rapid Tests, Advantages
 Increase access to
 Test time under 30 minutes
prevention
 Most require no refrigeration
 Support increased number of
testing sites  None or one reagent
 Encourage self-testing  Minimal or no equipment
 Same-day diagnosis and required

counseling  Minimum technical skill

 Robust and easy to use  Ability to use whole blood

The Ethiopian Public Ministry of Health-Ethiopia

17
Health Institute
 HIV rapid tests disadvantages
 Small numbers for each test run

 Quality Assurance/Quality Control at multiple sites

 Test performance varies by product

 Reader variability in interpretation of results

 Limited end point stability of the results

 Need refrigerator to store the kits Eg Capilus

The Ethiopian Public Ministry of Health-Ethiopia

18
Health Institute
 Enzyme immunoassays (EIAs)
 EIA is a quantitative assay that measure HIV
Ab.
 Most EIAs can detect antibodies to HIV-1 and
HIV-2.
 Here is how EIA works:

Sample is added to micro well plate that has

been coated with HIV antigen(s)
After a series of reagent additions,
incubations and washings, the plate is
The
placed in reading
reading device device.
measures the optical density of color that developed

The Ethiopian Public Ministry of Health-Ethiopia

19
Health Institute
 Virological assays
 HIV DNA PCR is the most widely used initial assay for early infant
diagnosis.

 HIV RNA PCR and other nucleic acid detection techniques assist in
clinical management.

 P24 Core protein- Used for the diagnosis of pediatric HIV-1

infections and blood bank safety (high incidence countries)
Can be detected,
 2 to 3 weeks after HIV infection
About 6 days before antibody tests become
The Ethiopian Public reactive
Ministry of Health-Ethiopia
20
Health Institute
 Complexity of HIV Tests
• .

Activity 2.2. Self-Reflection

Instruction: Reflect your ideas on the following
question.

What are the basic criteria to categorize the

complexity of HIV tests

Time: 3 minutes

The Ethiopian Public Ministry of Health-Ethiopia

21
Health Institute
 Complexity of HIV Tests
 Varies, level 1 to level 4, in terms of
equipment and technical skill.

Level 1: No additional equipment and little

or no laboratory experience needed

Level 2: Reagent preparation or a multi-step

process is required; centrifugation or optimal
equipment

Level 3: Specific skills such as diluting are required

Level 4: Equipment and trained laboratory technician are required
The Ethiopian Public Ministry of Health-Ethiopia
22
Health Institute
 Challenges of HIV Testing
 The ability of some test to detect early infections is suboptimal.

 Specialized testing is required to diagnose HIV infection in infants

younger than 18 months.

 Some tests may not be able to detect antibodies produced against

specific HIV subtypes.

 Cross reactivity with other health conditions or infections

 Some technologies require specific equipment that must be properly

maintained.

 Personnel need a certain level of skill to accurately perform and

The Ethiopian Public Ministry of Health-Ethiopia
interpret tests varies (from minimal23 to high level
Health Institute
 Chapter Summery
• Spectrum of HIV Diagnostic categorized as serological and
Virological assays

• Serological HIV testing technologies characterized as rapid

and EIA.

• There are three formats of HIV Rapid tests

The Ethiopian Public Ministry of Health-Ethiopia

24
Health Institute
 References:
1) Consolidated guidelines on HIV prevention, testing, treatment, service
delivery and monitoring: recommendations for a public health approach.
Geneva: World Health Organization; 2021. Licence: CC BY-NC-SA 3.0 IGO

2) Consolidated guidelines on HIV testing services, 2019. Geneva: World

Health Organization; 2020. Licence: CC BY-NC-SA 3.0 IGO.

3) Web Annex I. In vitro diagnostics for HIV diagnosis. In: Consolidated

guidelines on HIV testing services, 2019. Geneva: World Health
Organization; 2020. Licence: CC BY-NC-SA 3.0 IGO.

4) WHO, Guidance note on the selection of technology for the early diagnosis
of HIV in infants and children
The Ethiopian Public Ministry of Health-Ethiopia
25
Health Institute
.

QUESTIONS????

The Ethiopian Public Ministry of Health-Ethiopia

26
Health Institute