ZOOL 143 Topic 7 Detection of HIV Infection 1

EGERTON UNIVERSITY
COLLEGE OF OPEN AND DISTANCE LEARNING

E-CAMPUS
ZOOL 143: Biology of HIV/AIDS and Society
Topic 7 Handout
Copyright
Copyright© Egerton University
Published 2020
All rights reserved. No part of this publication may be reproduced, stored in a
retrieval system or transmitted in any form or by any means, electronic, mechanical,
photocopying, recording, or otherwise, without the prior written permission of the
copyright owner.
"Transforming Lives through Quality Education"

Page 1 of 10
Topic Seven: Detection of HIV Infections
Introduction
Welcome to topic seven. As you are now aware HIV infection has very long
asymptomatic latency period, it is difficult for one to know his/her HIV status. A
laboratory test is the only diagnostic tool for confirming presence of HIV particles
in a person. In this topic we shall learn about the HIV detection techniques,
models of services and counselling associated with HIV testing processes.
Learning Outcomes
By the end of this topic you should be able to:
i. Describe the methods for detecting HIV in patients

ii. Discuss the importance of testing and counselling.
iii. Explain the models of HIV testing services in Kenya.
7.1 Types of HIV Tests
a) What HIV Test Looks For
Detection of HIV infection does not necessarily look for HIV particles in blood,
but either antibodies against HIV or HIV antigen such as p24 protein or HIV RNA
or proviral DNA. These elements become detectable after a period of time since
infection although the immune system begins to produce antibodies once HIV
enters the body. The period before that is termed "window period", and the HIV
test show negative although the person can infect others.

Page 2 of 10
symptoms symptoms
HIV DNA
HIV Abs
‘window
’
HIV load
HIV-1 p24
antigen
0 1 2 3 4 5 6 / 2
1°infxninfecti4 6
week 8 10 year
on Time following
s s
infection
Figure 7.1: Clinical course of HIV antibody and antigen appearance (Source:
CDC, 2013)
b) HIV Antigen Tests
These are used to detect p24, the core protein of HIV, before Abs can be detected
(i.e. in 2 to 3 weeks after infection. It is useful in diagnosis of pediatric HIV-1
infections as well as checking blood bank safety (high incidence countries).
c) HIV Antibody Tests
Tests most commonly used to diagnose HIV infection are those that detect HIV-1
antibodies. There are three best-known HIV antibody tests: the ELISA (enzyme-
linked immunosorbent assay); the Western Blot tests; and the HIV Rapid tests.
i) HIV ELISA Tests
The best tests to detect HIV antibodies are the ELISA tests, which are
extremely accurate in reacting to the HIV antibodies that are formed by the
immune system in an unsuccessful attempt to protect the body against the
virus.HIV antibodies can usually be detected in the blood four to six weeks
after infection. The antibody tests will therefore only become positive
approximately six weeks after infection.
The ELISA HIV antibody test is the most popular and commonly used
laboratory test because it is very sensitive, reliable and produces very few
false negative results, and is reasonably cheap. To make the diagnosis even
Page 3 of 10
more accurate, a sample that is found to test positive with one ELISA test
will usually be re-tested with a second, different ELISA test.
ii) Western Blot Test
Western Blot is a more specific confirmatory test after ELISA test. It reacts
to the presence of antibodies of specific elements of the HIV particle, such
as gp120, g41 and p24. Since it relies on detection of antibodies to multiple
parts of HIV particle to confirm a positive result, it is more reliable and less
prone to giving false results.
iii) HIV Antibody Rapid Tests
A rapid HIV antibody test is a blood test based on latex agglutination, red
cell agglutination, or dip stick. All positive rapid HIV results should,
however, always be confirmed with a second rapid test (from another batch)
or with a laboratory-based EIA antibody test.
Advantages of rapid tests are:
• Increases access to prevention (VCT) and interventions (PMTCT)

• Supports increased number of testing sites
• Same-day diagnosis and counselling
• Robust and easy to use
• Test time under 30 minutes
• Most require no refrigeration
• None or one reagent
• Minimal or no equipment required
• Minimum technical skill
The disadvantages of rapid test are:
• Small numbers for each test run

• Quality Assurance/Quality Control at multiple sites
• Test performance varies by product
• Refrigeration required by some products
• Reader variability in interpretation of results
• Limited end-point stability of test results

Page 4 of 10
The design for rapid test kits format is lateral flow strip. Rapid test devices
approved include OraQuick, UniGold, Determine, and HemaStrip.
Add Sample
Test Control
Conjugate line
Line
IgG Abs Colloidal gold HIV antigen Anti-IgG/gold

HIV antibodies conjugated to HIV antibodies
antigen
Figure 7.2: Format for rapid test device (Source: CDC, 2005)
Figure 7.3: Commonly used rapid test kits: Oraquick, Unigold and
Determine (Source: CDC, 2005)
7.2 HIV Testing and Counselling (HTC) Services
a) Importance of Counselling
HTC services involve both testing and counselling. Counselling is a systematic

process which gives individuals an opportunity to explore, discover and clarify
ways of living more resourcefully with greater sense of being. Counselling may
be concerned with addressing and resolving a particular problem, making
decisions, coping with crises, working through conflict, or improving relationships

Page 5 of 10
with others. Counselling can comfort, ease suffering, heal psychological wounds,
and act as sounding board for moving forward.
b) Advantages of HIV Testing
i. Access to appropriate treatments for HIV-positive individuals early in

the infection can delay the onset of AIDS and prolong survival.
ii. Detection of infection at an asymptomatic stage may avoid a range of
severe physical and social complications.
iii. A negative test result can relieve anxiety after perceived exposure to
infection.
iv. A positive result encourages an individual to make important decisions
and lifestyle changes that improve their health status and life
expectancy.
v. Widespread testing helps to determine the extent and distribution of
infection, which in turn can assist in planning for support and prevention
strategies.
vi. Discordant couples can be encouraged to practice safe sex and safe drug
use, to prevent the spread of infection between the positive and negative
partners.
c) Process of Counselling
i) Informed Consent
Before HIV test is undertaken, informed consent should be obtained. One way the
counsellor can tell that one is ready for the test is when he/she is ready to share the
results with someone, e.g. mother, spouse, friend. Testing without consent
constitutes an assault (unless authorized by the law).
ii) Pre-Test Counselling
Individual pre-test counselling must precede all HIV testing. Some of the key
points in pre-test counselling in adults are:
i. ensure the person understands the basics about HIV/AIDS,

Page 6 of 10
ii. explain the meaning of HIV test, its procedure and what the
results mean,
iii. explain clearly the risks and benefits of knowing your HIV status,
iv. provide a chance to discuss your fears, worries and anxieties and
encouragements,
v. explain guarantees of confidentiality and,
vi. explain the need for support.
iii) Post-Test Counselling
All clients should receive post-test counselling irrespective of HIV results. The
content of post-test counselling will be guided by the HIV test results. It is to:
i. ensure that the person understands the implications and meaning of the
results;
ii. handle better the anxiety and fear associated with impending receipt and
possible consequences of the results;
iii. agree to a follow-up plan if HIV positive, or to a second test if HIV
negative;
iv. agree to post-test lifestyle changes that reduce risk of HIV infection or
guarantee protection or guarantee protection and;
v. discuss available HIV management options.
iv) Confidentiality
HTC programmes are elaborately designed to ensure that confidentiality is

maintained. Information about one person should not be disclosed to another,
except: i) where another person has a need to know (e.g. a health service
provider) and, ii) where required by law (e.g. notifiable diseases).
7.3 Models of HTC Services
There are two models used in HTC, namely VCT (voluntary counselling and
testing) and PICT (Provider-initiated counselling and testing) services.
a) VCT

Page 7 of 10
Voluntary Counselling and Testing (VCT) is the uncoerced accessing of HIV
testing and counselling services by people who want to know their HIV status.
The goals of VCT are:
• Prevention of HIV transmission.

• Early uptake of services. E.g. Counselling for positive living, Social
support, Legal advice, Future planning
• Societal benefits: Normalisation of HIV, Reduction of stigma, Promote
awareness, Support human rights
• Increase adherence to: ARV therapy, Preventive therapies, ARV
regimens for PMTCT, Infant feeding choices
Barriers to VCT services include:
• Fear,
• No cure or treatment,
• Stigma,
• No need since I’m faithful,
• Partner with a negative HIV result,
• Gender inequalities,
• Lack of perceived benefit,
• Lack of access to care and support services
b) PICT
Many people in SSA do not know their HIV status since uptake of VCT has been
suboptimal. Provider-initiated counselling and testing (PICT) has been introduced
to ensure that HCT becomes the standard of care in all consultations with health
providers. This is because the relationship between medical practitioners and their
patients provides an ideal situation to offer patient-centred care, allowing for
routine HIV counselling and testing.
c) Similarities between PICT and VCT
• Both are voluntary and require consent from the client.

• Testing is always performed in the client’s best interests, in keeping with
acceptable principles of medical ethics.
• HIV results are always reported back to the client.
• In both models the client is supported to deal with the HIV test results.

Page 8 of 10
• Counselling always precedes and follows testing.
d) Differences between VCT and PICT
PICT VCT
When seeking medical care Individual chooses to seek

and HCT is recommended and HCT
performed by medical
practitioner as part of the
consultation
Services provided are Anonymous or

confidential and documented confidential services may
in medical record to ensure be offered
continuity of care
Primary focus is on Primary focus is on

identifying HIV-infected preventing HIV
people and linking them with acquisition through risk
prevention, care and treatment assessment, risk reduction
services and testing
Verbal consent is required and Verbal consent is required

should be documented in the but not documented
patient record
First user of the test result is First user of the test result
the health care worker to is the client, who uses the
make a correct diagnosis and information to make
provide appropriate treatment personal life decisions
Topic Summary
In this topic we have learned that:

Page 9 of 10
• Detection of HIV infection looks for antibodies against HIV or HIV antigen
such as p24 protein or HIV RNA or proviral DNA. Most commonly used
detection tests are antibody tests as well as antigen tests. Antigen tests are
used to detect p24, the core protein of HIV, especially in children before
antibodies can be detected. The most common antibody test is the rapid test
is a blood test based on latex agglutination, red cell agglutination, or dip
stick.
• HIV testing and counselling promotes safe sex, self-confidence and

reduction of HIV transmission. The testing process involves informed
consent, pre- and post –test counselling, actual testing. Confidentiality is
maintained. Two HCT models are used in Kenya are VCT and PICT.

Page 10 of 10

ZOOL 143 Topic 7 Detection of HIV Infection 1

Uploaded by

Copyright:

Available Formats

ZOOL 143 Topic 7 Detection of HIV Infection 1

Uploaded by

Document Information

Original Description:

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

ZOOL 143 Topic 7 Detection of HIV Infection 1

Uploaded by

Copyright:

Available Formats

EGERTON UNIVERSITY

COLLEGE OF OPEN AND DISTANCE LEARNING

ZOOL 143: Biology of HIV/AIDS and Society

"Transforming Lives through Quality Education"

By the end of this topic you should be able to:

i. Describe the methods for detecting HIV in patients

7.1 Types of HIV Tests

a) What HIV Test Looks For

"Transforming Lives through Quality Education"

b) HIV Antigen Tests

c) HIV Antibody Tests

i) HIV ELISA Tests

ii) Western Blot Test

iii) HIV Antibody Rapid Tests

Advantages of rapid tests are:

• Increases access to prevention (VCT) and interventions (PMTCT)

The disadvantages of rapid test are:

• Small numbers for each test run

"Transforming Lives through Quality Education"

IgG Abs Colloidal gold HIV antigen Anti-IgG/gold

7.2 HIV Testing and Counselling (HTC) Services

HTC services involve both testing and counselling. Counselling is a systematic

"Transforming Lives through Quality Education"

b) Advantages of HIV Testing

i. Access to appropriate treatments for HIV-positive individuals early in

ii) Pre-Test Counselling

i. ensure the person understands the basics about HIV/AIDS,

"Transforming Lives through Quality Education"

iii) Post-Test Counselling

HTC programmes are elaborately designed to ensure that confidentiality is

7.3 Models of HTC Services

"Transforming Lives through Quality Education"

• Prevention of HIV transmission.

Barriers to VCT services include:

c) Similarities between PICT and VCT

• Both are voluntary and require consent from the client.

"Transforming Lives through Quality Education"

d) Differences between VCT and PICT

When seeking medical care Individual chooses to seek

Services provided are Anonymous or

Primary focus is on Primary focus is on

Verbal consent is required and Verbal consent is required

In this topic we have learned that:

"Transforming Lives through Quality Education"

• HIV testing and counselling promotes safe sex, self-confidence and

"Transforming Lives through Quality Education"

You might also like