Afifah x Finalise SEMINAR IIUM

8/4/2019 Afifah x Finalise SEMINAR IIUM

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UNAIDS main objectives

screening of donated blood

epidemiological surveillance of HIVprevalence or trends

diagnosis of infection in individuals.


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DIAGNOSIS

Screeningassays

Tests to ConfirmHIV Infection


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Who?

Mandatory

Muslim brides

Prisoners-drug addicts

Entrance test-Pusat Serenti

Recommended

pregnant women

Persons at high risk for HIV infection


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WHO policy on HIV Testing for children and

young infants

Orphans and vulnerable children (includingstreet children)

Children before adoption

Infants who have been abandoned

Children who have been sexually abuse

Children living in child-headed household

Children living in custodial guardians


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Where?

Available in all government clinics and hospitals

FOR FREE

Available in private clinics and hospitals.


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HIV Screening Assays


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Immunologic Principle

particle agglutination,

immunodot (dipstick),

immunofiltration (flow-through device),

immunochromatography (lateralflow)


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FDA-Approved Rapid HIV Antibody Screening Tests

February 2008

OraQuick ADVANCE RapidHIV-1/2 Antibody Test

Uni-Gold Recombigen HIV

Reveal G-3 Rapid HIV-1

Antibody Test

MultiSpotHIV-1/HIV-2 Rapid

Test

ClearviewHIV 1/2 STAT-PAKClearviewCOMPLETE HIV1/2


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Rapid Test


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Rapid Test


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Rapid Test


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Rapid test in Malaysia

Results of this test can be obtained in less than

15 minutes.

This test had to go through the scrutiny of the

Malaysian Institute of Medical Research

before being accepted for use at health clinics.

The Rapid Test has a sensitivity and specificity of

between 99.8% and 99.9%.


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Advantage

Good for testing 1 to 100specimens at a time

Requires minimal equipment and

reagents

Can be performed in a clinic (on-

site testing)

Highly skilled staff not required

Very easy to interpret test results

Results in < 45 minutes Test kits

can be stored at room temperature(increased stability)

Limitations

Not good for testing >100specimens at a time

The QA/QC is performed at

multiple sites: requires morecontrol

May cost more perindividual testthan EIA

Choice of testing strategy mayrequire multiple specimens

Interreader variability may provideinconsistent results with someassay formats (e.g.,particleagglutination)


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Tests to Confirm HIV Infection


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Methodology

-electrophoretic technique to separate HIV antigens derivedfrom a lysate of virus grown in culture

-("blotted") to nitrocellulose paper

-paper is cut into thin strips (each with the full distribution of

viral protein antigen bands)-incubated with a 1:50 or 1:100 dilution of a test sample or a

control

-Washed~incubated with a labeled (tagged) antihumanglobulin

-enzyme (horseradish peroxidase or alkaline phosphatase)react with antigen-antibody complex

-band formed


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Classification of HIV-antibody status

Positive Negative

Indeterminate


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Positive

For positive classification

CDC guidelines-which require reactivity to at

least 2 of the following antigens

p24, gp41, gp120/160


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Negative

For negative classification

Absence of all bands

Exception for WHO-that results also can be reported as negative if

there is only a very weak p17 band


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Indeterminate

For indeterminate classification

-is reactivity to 1 or more antigens, but not

fulfilling the criteria for positivity

-indeterminate results show only weak reactions

to the Gag proteins (mostly p17, p24 and/or

p55)


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Indeterminate WB result

- WHO recommends retesting persons after 2

weeks,

-while other organizations suggest waiting 1-6

months before retesting


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Retest result

negative or the bandprofiles do not progress

progress serologically(more bands or greaterintensity of bands) orconverts to positive

(seroconversion)

* individuals who have received vaccination for HIV (eg, subunit gp160) may be

misidentified as positive based on reactions to the envelope antigens alone


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Cause

hypergammaglobulinemia,

the presence of cross-reactive antibodies,

infection by HIV-2,

infection by an unknown (but related retrovirus)

* autoimmune diseases (eg, systemic lupus erythematosus) can cause false-positive HIV tests


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Limitations

Nonquantitative

Training

It is complex to administer and may produceindeterminate results if a person has a

transitory infection with another virus.


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the initial and second tests must be of different

principle (bead vs microtiter) and/or use a

different antigen source (lysate vs

recombinant or synthetic peptide).


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HIV Diagnosis Dilemmas

1) indeterminate Western blot results;

2) Minimally Reactive Western Blot Results

3) inconsistent results when repeating specimens

or testing follow-up specimens;4) the occurrence of technical errors;

5) false-negative results due to HIV Group Oviruses;

6) laboratory diagnosis of HIV infection in thenewborn.


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Indeterminate Western Blot Results

Solutions

-Retesting- follow-up specimen in 1-3 months

- IFA, PCR, viral culture, or other antigen assays


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Minimally Reactive Western Blot

Results

In these cases, it is important to note on the

report form that "on rare occasions, this

profile has been found in persons who are not

infected, and submission of a new specimen inseveral weeks is recommended."


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inconsistent results

Due-mislabeling or technical errors.

Solution

Investigation through quality assurance

monitoring


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Technical Errors

Solution

-dedicated supervisory review mechanism

-Outline the quality assurance measures


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False-Negative Results for HIV Group O

Cause

infected by HIV Group O viruses

Solution

Health care providers can be vigilant by

inquiring as to the geographic origin ofpersons tested, or their contact with persons

from these areas of Africa


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Diagnosis in the Newborn


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HIV test use for managing therapy

Viral Load


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Viral Load technique

The PCR (polymerase chain reaction) method uses an enzymeto multiply the HIV in the blood sample. Then a chemicalreaction marks the virus. The markers are measured andused to calculate the amount of virus. Roche and Abbottproduce this type of test.

The bDNA (branched DNA) method combines a material thatgives off light with the sample. This material connects withthe HIV particles. The amount of light is measured andconverted to a viral count. Bayer produces this test.

The NASBA (nucleic acid sequence based amplification)method amplifies viral proteins to derive a count. It ismanufactured by bioMerieux.


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Summary

Malaysia

Rapid Test

Western Blot

*PCR for infants and children

Documents

Afifah x Finalise SEMINAR IIUM