low (less than 1% of all samples). 3. Since Virutex is only a quick screening test, for confirmation of the results, a confirmatory test should

 

Blood containing hepatitis B virus (HBV) is potentially

infectious. In most cases, detectable levels of hepatitis B

surface antigen (HBsAg) circulate in the bloodstream of

an infected person, 2 to 3 weeks prior to the appearance

of clinical symptoms. These levels are especially elevated

in the symptomatic phase, thereafter the levels slowly

decline. Detection of HBV using HBsAg as a marker to

screen blood donors is essential to reduce the risk of

transmission of hepatitis B by blood transfusion.

Reagent

1. Virutex HBsAg reagent A uniform suspension of

polystyrene latex particles coated with IgG class of

monoclonal Anti-HBsAg antibodies.

2. Positive control, reactive with the Virutex latex reagent.

3. Negative control, nonreactive with the Virutex latex

reagent.

Virutex HBsAg reagent conforms to the sensitivity

requirements of a “Third generation” test. Each batch of

reagent undergoes rigorous quality control at various

Serology/Immunology 663

stages of manufacture for its specificity, sensitivity and

performance.

Reagent Storage and Stability

1. Store the reagent at 2 to 8°C. Do not freeze.

2. The shelf life of reagent is as per the expiry date

mentioned on the reagent vial label.

Principle

Latex particles coated with anti-HBsAg antibodies will

agglutinate when mixed with serum or plasma containing

hepatitis B surface antigen within the detectable levels.

Agglutination is absent when the hepatitis B surface

antigen is absent or not within the detectable levels.

Note

1. In vitro diagnostic reagent for laboratory and

professional use only. Not for medicinal use.

2. All the reagents derived from human source have been

tested for HBsAg and anti-HIV antibody and are found

to be non-reactive. However, handle the material as if

infectious.

3. Reagent contains sodium azide 0.1% as preservative.

Avoid contact with skin and mucosa. On disposal,

flush with large quantities of water.

4. The reagents can be damaged due to microbial

contamination or exposure to elevated temperatures.

It is recommended that the performance of the

reagents be verified by testing with the negative or

positive controls provided with the kit.

5. Shake the latex antigen vial gently before use to

disperse the latex particles uniformly and improve the

test readability.

6. Use only a thoroughly clean and dry glass slide. Clean

the slide with distilled water and wipe dry before use.

7. Accessories provided with the kit only must be used

for optimum results.

Sample Collection and Storage

No special preparation of the patient is required prior to

sample collection by approved techniques. Do not use

hemolyzed samples. Though plasma may be used, fresh

serum is preferable. In case of delay in testing, store the

samples at 2 to 8°C for up to 24 hours.

Material Provided with the Kit

Reagent Pack

Latex reagent coated with anti-HBsAg antibody, positive

control reactive with the latex reagent, negative control

nonreactive with the latex reagent.

Accessories Pack

Glass slide with six reaction circles, mixing sticks, rubber

teats, sample dispensing pipettes.

Additional Material Required

Test tubes (10 × 75 mm), pipettes, isotonic saline,

stopwatch, direct light source.

Procedure

Bring reagent and samples to room temperature before

testing.

1. Pipette one drop of sample to be tested onto one of

the reaction circles of the glass slide using a sample

dispensing pipette, provided with the kit.

2. Prepare a 1:40 dilution (0.05 mL serum + 1.95 mL

isotonic saline) of samples to be tested in isotonic saline.

3. Pipette one drop of the diluted sample on the next

reaction circle of the glass slide.

3a. In steps 1 and 3 above, carefully aspirate the sample

into the dispensing pipette avoiding sample entering

the rubber teat and subsequent cross contamination.

4. Place one drop of positive and negative control onto

the remaining reaction circles of the slide (do not

dilute controls).

5. Shake the latex reagent vial gently to uniformly disperse

the reagent suspension. Add one drop of the latex

reagent to each of the samples and controls on the slide.

6. Mix with separate mixing sticks, spreading the mixture

uniformly over the entire reaction circle.

7. Immediately start a stopwatch. Rock the slide

gently back and forth, observing for agglutination

macroscopically at 5 minutes.

Interpretation of Results

1. No agglutination with diluted and neat samples is a

negative test result: HBsAg absent.

2. Agglutination with neat sample but no agglutination

with diluted sample is a positive test result: HBsAg

present (weak positive).

3. Agglutination with both neat and diluted samples

is a positive test result: HBsAg present (moderate

positive).

4. Agglutination with diluted sample but no agglutination

with neat sample is a positive test result: HBsAg

present (strong positive).

Remarks

1. The positive control has been inactivated at 60°C for

10 hours and is not expected to be infectious.

664 Concise Book of Medical Laboratory Technology: Methods and Interpretations 2. Presence of autoantibodies such as RF and heterophile

antibodies may interfere with the test giving a false

positive result. Probability of such an occurrence is

low (less than 1% of all samples).

3. Since Virutex is only a quick screening test, for

confirmation of the results, a confirmatory test should

be used.

4. Positive and negative controls should be run with each

series of tests and the results compared with unknown

specimens to distinguish possible granularity from

agglutination.

5. It is recommended that results of the tests should be

correlated with clinical findings to arrive at the final

diagnosis.