Question from S 10 Flashcards
Official exam question - will be on 2024 exam
12 month old child presents to paeds assessment unit with 4 day history of fever, coryza, SOB, inflamed pharynx and conjunctivita, maculopapular rash
What 3 tests would you send?
Oral fluid swab -
- Rubella IgM/ IgG/ RNA
- Measles IgM/ IgG/ RNA
Nose/throat combination swab in VTM
- extended viral respiratory PCR
Clotted blood sample for serology
- Rubella IgM/ IgG
- Measles IgM/ IgG
- Parvo B19 IgM/ IgG
- CMV IgM/ IgG
- EBV IgM/ IgG
Consider if travel history:
Dengue, Zika, Chikungunya
exam question - will be on exam
Measles RNA testing
What is the target of RNA testing?
Measles H gene - haemagglutinin
Wild-type measles viruses have been divided into eight clades containing 24 genotypes based on the nucleotide sequences of their hemagglutinin (H) and nucleoprotein (N) genes, which are the most variable genes in the viral genome.
exam question - will be on exam
Case 1
IgG 5
C/O 13
IgM 3.9
C/O >1
Oral fluid swab H gene PCR
CT 26
C/O 35
MS2 Bacteriophage DNA
CT 24
C/O 35
Human Ribonuclease P gene
CT 23
C/O 35
What is the importance of MS2 bacteriophage
MS2 bacteriophage DNA is used to spike the sample, and act as an internal control.
It ensures there is efficient nucleic acid extraction, and no PCR inhibition
exam question - will be on exam
Case 1
IgG 5
C/O 13
IgM 3.9
C/O >1
Oral fluid swab H gene PCR
CT 26
C/O 35
MS2 Bacteriophage DNA
CT 24
C/O 35
Human Ribonuclease P gene
CT 23
C/O 35
What is the importance of Human Ribonuclease P gene
Human Ribonuclease P gene is a host target. This is used to control for adequate host material in the initial sample
exam question - will be on exam
Case 1
IgG 5
C/O 13
IgM 3.9
C/O >1
Oral fluid swab H gene PCR
CT 26
C/O 35
MS2 Bacteriophage DNA
CT 24
C/O 35
Human Ribonuclease P gene
CT 23
C/O 35
What are the possible clinical interpretations of these results?
MS2 Bacteriophage detected - passed
Human Ribonuclease P detected - passed
controls accepted
IgM detected
IgG not detected
RNA detected
consistent with an acute Measles infection
Measles definitely be on exam
Case 1
IgG 5
C/O 13
IgM 3.9
C/O >1
Oral fluid swab H gene PCR
CT 26
C/O 35
MS2 Bacteriophage DNA
CT 24
C/O 35
Human Ribonuclease P gene
CT 23
C/O 35
What further information would you like?
MMR history - recent vaccine may give similar picture, and can cause a Measles-like illness
Exposure - any close contacts with a rash
Foreign travel
Immunosuppression
Pregnancy
exam question - will be on exam
Case 1
IgG 5
C/O 13
IgM 3.9
C/O >1
Oral fluid swab H gene PCR
CT 26
C/O 35
MS2 Bacteriophage DNA
CT 24
C/O 35
Human Ribonuclease P gene
CT 23
C/O 35
What is the initial management of this patient?
Notify IPC -
Admit to negative pressure side room
FFP3 mask/ gown/ visor/ gloves
Notify public health for contact tracing
Notify occupational health for staff tracing
Vitamin A 2x doses for all children admitted with severe Measles
exam question - will be on exam
Case 2 - 2 year old child
IgG >300
C/O 13
IgM 0.98
C/O >1
Oral fluid swab H gene PCR
CT 37
C/O 35
MS2 Bacteriophage DNA
CT 25
C/O 35
Human Ribonuclease P gene
CT 23
C/O 28
What are the possible clinical interpretations of these results?
What further testing would you order?
MS2 Bacteriophage detected - passed
Human Ribonuclease P detected - passed
controls accepted
IgM equivocal
IgG detected - strongly positive
RNA detected - very low level
- recent immunisation
- recent breakthrough infection - child has only had 1xMMR dose. So could develop an infection. Send PCR testing to Colindale for Measles typing
- answer could be obtained through further history:
- any recent immunisation
- any recent travel/ epidemiological link to infection
When do children get their MMR vaccines?
1 year
3 years and 4 months
exam question - will be on exam
Case 3
Oral fluid swab H gene PCR
CT 40
C/O 35
MS2 Bacteriophage DNA
CT 25
C/O 35
Human Ribonuclease P gene
CT 40
C/O 28
What are the possible clinical interpretations of these results?
MS2 Bacteriophage detected - passed
Human Ribonuclease P not detected - failed
controls failed
Cannot reliably exclude a Measles infection, as the PCR was not successful due to inadequate sample quality.
Low level Measles RNA could be because of poor sample quality, but could also be due to an early infection
Suggest getting a repeat sample
exam question - will be on exam
Assessing Measles contacts
What are the important parts of the history?
Infectious period is 4 days before rash, to 4 days after rash
Exposure:
Household
Face-face (<2M)
Same room 15 mins
Large room for prolonged time e.g hospital bay
Patients:
MMR history - age born before 1970 assume immune
Immunosuppression
Pregnancy
Infants <12 months old
In what decade of birth should we assume that patients are immune to Measles?
If born before 19070 assume immune
exam question - will be on exam
Immunosuppressed Measles contact
What categories do we divide patients in to?
What are examples?
Group A
- those who are should develop and maintain adequate antibody response from past exposure or vaccination
Group B
- those who lose or may not maintain adequate antibody response
e.g BMt, leukaemia
exam question - will be on exam
Immunosuppressed Measles contact
Group A
What is the management?
All ages
Born before 1970
Born between 1970-1990
Born after 1990
Previous Measles IgG pos - assume immune
Previous Measles infection - assume immune
Born before 1970 (without Measles IgG result), and history of Measles infection - assume immune
Born before 1970 (without Measles IgG result), and no history of Measles infection - check IgG
Born between 1970 and 1990 (without Measles IgG result), and history of Measles infection - check IgG
Born between 1970 and 1990 (without Measles IgG result), and no history of Measles infection or vaccination - check IgG
Born after 1990 (without Measles IgG result), and history of 2xMeasles vaccines - check IgG
Born after 1990 (without Measles IgG result), and history of 1xMeasles vaccines - check IgG
Born after 1990 (without Measles IgG result), and history of no Measles vaccines - give IVIG
https://assets.publishing.service.gov.uk/media/653b880ae6c9680014aa9c1f/national-measles-guidelines-october-2023.pdf page 28
exam question - will be on exam
Immunosuppressed Measles contact
When does HNIG need to be given?
Give within 72 hours, up to 6 days
incubation period Measles is 7 days
exam question - will be on exam
Immunosuppressed Measles contact
You wish to do Measles IgG to see if they are immune.
However this result will not be back before day 6
What action would you take>
If cannot get test results and give IVIG within 6 days, then just give IVIG as soon as possible
exam question - will be on exam
Immunosuppressed Measles contact
Group B
What is the management?
B(I)
- Measles IgG positive since treatment completed - assume immune
- No documented Measles IgG since treatment completed - Measles IgG test
B(II)
- IVIG regardless of status
This includes BMT/ Leukaemia
exam question - will be on exam
Immunosuppressed Measles contact
Group B
You wish to test your contact for Measles IgG, but you will not have the test result within 6 days of exposure.
How will this affect your decision making?
Give IVIG regardless, if test result wont be back by 6 days after exposure
exam question - will be on exam
Pregnant Measles contact
What is the management?
- 2x MMR vaccines - assume immune
- 1x MMR vaccine - Measles IgG
- unvaccinated - Measles IgG
If Measles IgG not detected, then give HNIG
If cannot test and give HNIG within 6 days, then off HNIG
MMR cannot be given as teratogenic
exam question - will be on exam
Infant <12 month Measles contact
Why are they at high risk of infection?
Not had MMR vaccine yet
Maternal transplacental antibodies are low, and reduce quickly after birth
exam question - will be on exam
Infant Measles contact
How do you manage:
Infant <6 month old
assume susceptible and give HNIG regardless of maternal status
exam question - will be on exam
Infant Measles contact
How do you manage:
Infant 6-8 month old
Household exposure -
assume susceptible and give HNIG regardless of maternal status
Outside household exposure -
administer MMR within 72 hours
exam question - will be on exam
Infant Measles contact
How do you manage:
Infant >9 month old
give MMR vaccine within 72 hours
exam question - will be on exam
Adult unvaccinated Measles contact
What PEP would you offer?
If non-immune, give MMR vaccine
Does not need HNIG if not immunosuppressed or pregnant
exam question - will be on exam
What is SSPE?
Who is more at risk?
Rare, fatal, late complication of measles infection
Follows after infection in childhood, including after an unrecognised Measles infection.
Virus has been recovered from brains of patients who have died
1 case in every 25000 cases overall
Significantly higher risk if acquired earlier -
<2 year old rate is 1 in 8000
median interval is 7 years overall. Can range from 5 years to 30 years
exam question - will be on exam
WHO plan to eradicate Measles
Why is this possible?
Initial plan was to eradicate in 2005 - this failed
Only humans infected - no animal/ environmental reservoir
accurate, accessible diagnostics
effective vaccine - 90% 1 dose, 2x doses >95% effective
Evidence of effective transmission interruption as Measles cases worldwide have dropped - showed it is possible
exam question - will be on exam
IVIG dosing
What is the dose for immunosuppressed patients?
Immunosuppressed
0.15 g/kg
IVIG has high enough dose to be fully protective
exam question - will be on exam
IVIG dosing
What is the dose for pregnant contacts
Pregnant IVIG is not practical, as need IV access
Give HNIG 3000mg
exam question - will be on exam
IVIG dosing
What is the dose for infants
Infants IVIG is not practical, as need IV access
Give HNIG 0.6ml/kg up to maximum of 1000mg
exam question - will be on exam
What is difference between HNIG and IVIG?
IVIG is given IV - this is first line PEP for highest risk patients
HNIG is alternative. It is given IM if cannot give IV, or because it is not practical to give IV such as at a GP practice. Often used for pregnant/ infant contacts
HNIG will likely attenuate disease, but probably not terminate an infection, so not used in immunosuppressed patients
What PEP is required following inadvertent vaccination of Measles?
immunosuppressed - assess as usual. May need IVIG
Pregnancy - no PEP. But foetal follow up
MMR given 8 weeks after receiving blood products
What actions should be taken?
When MMR is given within three months of receiving blood products, such as immunoglobulin, the response to the measles component may be reduced.
This is because such blood products may contain significant levels of measles-specific antibody, which could then prevent vaccine virus replication.
Where possible, MMR should be deferred until three months after receipt of such products.
If immediate measles protection is required in someone who has recently received a blood product, MMR vaccine should still be given.
To confer longer-term protection, MMR should be repeated after three months
What are MMR contra-indications?
● pregnant women
● immunosuppressed
● anaphylactic reaction to a previous dose MMR vaccine
● anaphylactic reaction to neomycin or gelatine
Green book
What rare side effects are associated with MMR vaccine?
Febrile seizures
Rash - due to Measles or Rubella replication
Immune thrombocytopenia - thought to be due to Rubella
Arthropathy
