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Microbiology

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RNA Viruses

Question
73 out of 94
 

Specific test for HIV antibodies is:



A ELISA
B Southern blot test

C Northern blot test
D Western blot test

Ans. D Western blot test

Western blot is the most specific serological test for diagnosis of HIV infection

Strategies of HIV Testing

a. Strategy I: The serum is tested with one E/R/S test and if reactive, sample is considered positive and if non-reactive it is considered negative.

b. This strategy is used for transfusion safety. For this purpose, a highly sensitive and very reliable test kit must be used.

c. Strategy II: The serum reactive with one E/R/S test is retested with a second EIRJS test with higher specificity, based on a different antigen preparation and/or different test principle.

d. If found reactive on second E/R/S test also, it is reported as positive, otherwise as negative. This strategy is used for HIV surveillance.

e. Strategy III: The serum reactive with two E/R/S tests is retested with a third E/R/S test. The third test should again be based on different antigen preparation or test principle.

f. A serum testing reactive with all three E/R/S tests is reported positive.

g. A serum sample non-reactive in third E/R/S is considered equivocal borderline. Such individuals should be retested after three weeks. If this sample also provides an equivocal result, the person is considered to be HIV antibody negative.

h. For asymptomatic HIV infection, it is necessary to confirm the diagnosis with three tests. Symptomatic infections with opportunistic infections, however, may be subjected to two tests.

The first test selected for any of the strategies should be of highest sensitivity and second and third E/R/S test selected should be of highest specificity.

Fig: Determination of exposure code (EC)

Fig: Determination of HIV status code (HIV SC)

Table: Postexposure prophylaxis

EC

HIV SC

PEP Regimen

1

1

May not be required

1

2

Basic

2

1

Basic

2

2

Expanded

3

1 or 2

Expanded

Table - Basic and expanded regimens of post- exposure prophylaxis

BASIC REGIMEN

• Zidovudine 300 mg BD or 200 mg TOS for 4 weeks

• Lamivudine 150 mg BO for 4 weeks

EXPANDED REGIMEN

• Basic regimen + Indinavir 800 mg TOS for 4 weeks

RNA Viruses Flashcard List

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