Rubella Serology

Question 1

Other names for Rubella

Answer 1

“3-day” or “German” measles

Question 2

What type of infection is Rubella?

Answer 2

acquired infection

Question 3

Rubella symptoms

Answer 3

mild illness with

• rash on face, neck and trunk
• low fever

Question 4

Congenital Infections with Rubella:

• what will it cause in pregnant women
• how will it effect fetus specifically

Answer 4

• may cause fetal death or anomalies if pregnant women are infected
• fetus may have heart lesions, cataracts, skin lesions, hearing loss, others

Question 5

Chance of fetal involvement of rubella varies with stage of pregnancy. What %’s in 1, 2, 3, and >3 months?

Answer 5

1 month - 30-50%
2 month - 22-25%
3 month - 6-8%
>3 months - less frequent

Question 6

Why is rubella antibody testing used now in the U.S.?

Answer 6

Immune status determinations in

• healthcare workers (pre-employement)
• Premarital testing in some states
• women of child baring age

Question 7

4 reasons why rubella is usually diagnosed serologically?

Answer 7

1. virus difficult to grow in cell cultures
2. antigen testing not available
3. antibody determinations do not involve detecting virus or its antigens
4. Immune status: presence/absence of antibodies tells patients status

Question 8

What are the steps in the Passive (Hem)agglutination testing?

Answer 8

Add patients antibodies to antigen-coated carrier particles(latex particles) and if there is binding of Ag/Ab complex then you have agglutination

Question 9

GUIDELINES for Acquired Infections:

- collection (how many and when?)

Answer 9

Must have two serum specimens. One collected (acute) as soon as possible after onset, and second (convalescent) is collected 14 days later

Question 10

GUIDELINES for Acquired Infections:

- when is acquired infection confirmed?

Answer 10

if there is a fourfold or greater increase in antibody level

Question 11

GUIDELINES for Acquired Infections:
- what if there is no significant difference in antibody level and there is antibody present in the acute specimen (and collection is correct)?

Answer 11

Past rubella infection is indicated. This diagnosis can be made only when date of onset and date of acute specimen collection are within 2 or 3 weeks of each other

Question 12

GUIDELINES for Acquired Infections:

- What if acute specimen is collected several months after onset?

Answer 12

Newly produced IgG may have already increased fourfold or more but will now be at a steady level. No diagnosis can be made.

Question 13

GUIDELINES for Acquired Infections:

- what if no antibody is detected in either specimen?

Answer 13

the patient is negative for present or past rubella infection

Question 14

GUIDELINES for Congenital Rubella Infections:

- For what reasons do we test this?

Answer 14

For infants who are born with obvious congenital defect or for apparently normal infants born of mothers who had rubella during pregnancy

Question 15

GUIDELINES for Congenital Rubella Infections:

- How many specimen and what timeframe

Answer 15

Collect serum of infants at birth and at intervals during the first 6 months of life

Question 16

GUIDELINES for Congenital Rubella Infections:

- If antibody is present in the infants serum what does that mean?

Answer 16

means that the antibody may be produced by the infant in response to intrauterine infection OR may be maternal antibody

Question 17

GUIDELINES for Congenital Rubella Infections:

• How do you know if it is just the mothers antibody
• How do you know if its a real intrauterine infection

Answer 17

maternal antibody will be lost 5 to 6 months; therefore, persistence of (or increase in) antibody level up to and after 6 months indicate intrauterine infection.

Question 18

GUIDELINES for Congenital Rubella Infections:

- in pregnant women exposed to rubella, when should the specimen we collected?

Answer 18

within 10 days of EXPOSURE. To ensure that antibodies measured are “old” antibodies rather than newly produced antibodies the sample must be collected with 10 days of exposure.

Question 19

GUIDELINES for Congenital Rubella Infections:

- In pregnant women exposed, if antibody is present in serum collected within 10 days what does that mean?

Answer 19

the individual is immune due to past infection or immunization, fetus not at risk

Question 20

GUIDELINES for Congenital Rubella Infections:

- in pregnant women exposed, if no antibody is detected in serum collected within 10 days, what does that mean?

Answer 20

there is no evidence of immunity resulting from past infection or immunization. A second specimen should be collected 2 to 3 weeks and tested to determine if antibodies appear.