HIV-1 and HIV-2. This leads to the formation of colored band(s). The absence of colored band(s) in the test regions indicated the presence of antibodies to HIV-1/2 in the

 

Remarks

1. The addition of reagents must be accomplished

without interruptions.

2. After addition of the wash buffer, in step 7 of the

procedure, if the background in the reaction port is

high, the samples must be recentrifuged appropriately

so as to pellet invisible particulate matter. Test should

be rerun with the clear supernatant.

3. The presence of antibodies to HIV 1/2 indicates

previous exposure to HIV 1 and/or HIV 2 virus but

does not constitute a diagnosis of AIDS.

4. Absence of antibodies to HIV 1/2 does not indicate

that an individual is absolutely free of HIV 1 or HIV

2 as the collection of sample and its timing vis-a-vis

seroconversion will influence the test outcome.

5. Since HIV 1 and HIV 2 viruses are similar in genomic

structure and morphology and antibodies to them

have (30–70%) cross reactivity, reactive test bands

for HIV 1 and HIV 2 do not necessarily imply mixed

infection with HIV 1 and HIV 2.

6. Though Retroquick-HIV is a reliable and sensitive

screening test, it should not be used as a sole criterion

for diagnosis of HIV infection.

7. All positive specimen should be further tested using

appropriate supplemental confirmatory tests.

8. As in all tests the results must be correlated with

clinical findings before arriving at the final diagnosis.

9. Since various tests for HIV 1/2 differ in their

performance characteristics and antigenic

composition, the reactivity patterns may differ.

10. The results of Retroquic-HIV must be read within 30

minutes of test completion.

11. Do not compare the intensity of the test lines and

the control lines to judge the concentration of the

antibodies in the test sample.

12. Testing of pooled specimen is not recommended.

13. The control band in fresh unused membrane test

devices is blue colored and changes to blackish

purple color after test performance.

14. The control band would not develop if the sample

addition has not been done.

RAPID TEST FOR SIMULTANEOUS/DIFFEREN- TIAL DETECTION OF TOTAL ANTIBODIES TO

HIV-1 AND HIV-2 IN HUMAN SERUM/PLASMA

RETROSCREEN

(Courtesy: Tulip Group of Companies)

Retroscreen-HIV, is a rapid, self-performing, qualitative,

sandwich immunoassay for simultaneous and differential

detection of total antibodies, i.e. IgG, IgM, IgA etc to HIV-1

and HIV-2 virus in human serum/plasma.

672 Concise Book of Medical Laboratory Technology: Methods and Interpretations Summary and Explanation

Retroscreen-HIV is an immunochromatographic test for

simultaneous and differential detection of total antibodies

to HIV-1 and HIV-2 virus in human serum/plasma. Highly

purified recombinant antigens – gp41 and p24-O fusion

polypeptide, representing HIV-1 and HIV-1 group “O”

and synthetic peptide gp36 represeting HIV-2 are stripped

on the membrance as two separate test bands. An assay

control forms the third band. The same antigens are also

coated on colloidal gold. Synthetic gp36 is chosen instead

of recombinant gp36 to reduce cross-reactivity and enable

better discrimination between HIV-1 and HIV-2 samples.

Principle of the Assay

Retroscreen-HIV utilizes the principle of Immunochromatography, a unique two-site immunoassay on a

nitrocellulose membrane. The conjugate pad contains

four components – recombinant gp41 conjugated to

colloidal gold, recombinant p24-O conjugated to colloidal

gold, synthetic peptide gp36 conjugated to colloidal gold

and rabbit IgG conjugated to colloidal gold. As the test

specimen flows through the membrane test assembly, the

highly specific HIV-1/2 antigens-colloidal gold conjugate

complexes with the HIV-1/2 specific antibodies in the

specimen and travels on the membrane due to capillary

action along with the rabbit IgG-colloidal gold conjugate.

This complex moves further on the membrane to the test

region where it is immobilized by the HIV-1/2 antigens

coated on the membrane at two separate test regions for

HIV-1 and HIV-2. This leads to the formation of colored

band(s). The absence of colored band(s) in the test regions

indicated the presence of antibodies to HIV-1/2 in the

specimen.

The unreacted conjugate and unbound complex, if any,

move further on the membrane and are subsequently

immobilized by the anti-rabbit antibodies coated on the

membrane at the control region (C), forming a colored

band. This control band acts as a procedural control and

serves to validate the results.

Kit Components

Retroscreen-HIV kit has following components:

1. Device: Stripped with HIV-1 and HIV-2 specific

antigens and anti-rabbit IgG along with HIV specific

antigen and rabbit IgG gold conjugate. Each device is

individually pouched along with single-use sample

dropper and desiccant.

2. Sample running buffer: Buffer containing surfactant

and preservatives.

3. Instructions for use.

Storage and Stability

Retroscreen-HIV is stable up to the expiry date mentioned

on the label when stored at 4–30°C. Once the pouch is

opened, the device must be used immediately.

Material Required but not Provided

1. Disinfectant

2. Disposable gloves

3. Biohazard waste container.