Questions from S 2 Flashcards
What are other names for slapped cheek?
Parvo B19
5th disease
2 months old child with hepatitis
HHV6 detected as the cause
What is unique about this infection?
Most people have had infection previously, so would expect mother to transfer maternal antibody. So baby should be protected for 6-12 months. And acquire primary infection at aged 1-3
However, given evidence of infection early in life, this might suggest that this baby has chromosomally integrated HHV6. This was transferred by mother/father in the gametes
HHV6 inserts near telomeres in sperm/ egg, so 50% chance of passing on to child
2 month old child with hepatitis
HHv6 detected as the cause
How to test for potential chromosomally integrated HHV6?
Send EDTA whole blood and clot sample for HHV6 pcr
EDTA whole blood - has all cells, including cells with chromosomes, so will have high HHV6 viral load
Clot - serum and blood cells separate out. Will have significantly lower viral load
What is difference between blood plasma and blood serum?
- Serum sample has a clotting agent (clot sample). Fibrinogen clots together, and binds to RBCs removing them. This leaves a liquid portion - called the serum.
Serum is plasma minus RBC and fibrinogen
Useful for antibody tests as proteins left in the serum - Whole blood (EDTA sample)
Starting with whole blood, if an anticoagulant is added immediately after collection, then coagulation is prevented and all components are kept in suspension. If you just leave this blood sample alone without mixing, then all the components will settle out. The heavier cells will sink to the bottom. This results in a clear liquid at the top. This clear upper layer is plasma which is essentially all the components of blood minus the cells. Under centrifugation, a layer of white cells called the buffy coat forms between the plasma and red blood cells. Plasma retains fibrinogen.
Useful for PCR tests
You are running a haematology clinic with bone marrow transplant patients
Specify virological investigations for these cases
52 year old with vesicular rash extended from legs up to back
official question
Swab/ scraping/ scab
VZV
HSV
Entero
Mpox (Orthopox)
Other Orthopox - Vaccinia if has smallpox vaccine, Cowpox
Parapox - Orf
Electron microscopy
You are running a haematology clinic with bone marrow transplant patients
Specify virological investigations for these cases
72 year old 4 months post-bone marrow transplant. ALT 74
official question
serum/ plasma
HBsAg ELISA
EDTA
HCV RNA RT PCR
CMV PCR
Other
HAV RNA PCR
HEV RNA PCR
HSV PCR
VZV PCR
Adenovirus PCR
What is the case definition of Mpox?
official question
Possible case
a febrile prodrome compatible with mpox infection, where there is known prior contact with a confirmed case in the 21 days before symptom onset
an illness where the clinician has a suspicion of mpox, such as unexplained lesions, including but not limited to:
genital, ano-genital or oral lesion(s) – for example, ulcers, nodules proctitis – for example anorectal pain, bleeding
Febrile prodrome consists of fever ≥ 38°C, chills, headache, exhaustion, muscle aches (myalgia), joint pain (arthralgia), backache, and swollen lymph nodes (lymphadenopathy).
Probable case
A probable case is defined as anyone with an unexplained rash or lesion(s) on any part of their body (including genital/perianal, oral), or proctitis (for example anorectal pain, bleeding) and who:
has an epidemiological link to a confirmed, probable or highly probable case of mpox in the 21 days before symptom onset
or
identifies as a gay, bisexual or other man who has sex with men (GBMSM)
or
has had one or more new sexual partners in the 21 days before symptom onset
What is the mechanism of action of tecovirimat?
official question
P37 inhibitor
Tecovirimat inhibits the function of a major envelope protein
so virus cannot leave infected cell
What is the mechanism of action of cidofovir?
official question
Inhibits viral DNA polymerase
Cidofovir is a monophosphate nucleotide analog(cytosine).
After undergoing cellular phosphorylation to its diphosphate form, it competitively inhibits the incorporation of deoxycytidine triphosphate (dCTP) into viral DNA by viral DNA polymerase. Incorporation of the drug disrupts further chain elongation
You are running a haematology clinic with bone marrow transplant patients
Specify virological investigations for these cases
54 year old with haematuria
official question
Blood -
BK virus
Adenovirus
Urine
BK virus
You are running a haematology clinic with bone marrow transplant patients
2 year old with watery diarrhoea
official question
Stool -
Adenovirus
Rotavirus
Enterovirus
Parechovirus
Astrovirus
Calicivirus - Norovirus/Sapovirus
Blood- CMV
OCP - giardia, Crytosporidium
Different treatment of HSV infection.
What is treatment of HSV infection?
400mg 5x for simple infection
5mg/ kg TDS for severe infection or in immunocompromised
10mg/kg TDS for encephalitis
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How long does HIV survive in environment?
99% decay by 24 hours
likely survival time is a lot lower
What are methods to disinfect surfaces with HIV?
heat 60degC for 30 mins
standard germicide - 70% alcohol or 10% beach
pH extreme <6 or >10 for 10 mins
What is the link between HIV and other STIs?
Other STIs greatly increase the probably of HIV, and in fact help with increasing transmission
e.g HSV causes ulcers which can help transmission. HSV infection also recruits inflammatory which cells, which provides more CD4 cells for HIV to infect
From exposure to virus, what is the general path of viral spread in the body?
APC present to resting CD4 cells which become activated
CD4 cells move to lymph nodes and establish reservoir. Particularly early is the destruction of GALT
CD4 cells become depleted, and this stimulates production from bone marrow. Unfortunately this just creates a new population of susceptible cells
CD8 t-cells kill infected CD4 cells
CD4 cells produce some antibodies to fight HIV virus, and so viral load reduces quickly after first couple of weeks
In the asymptomatic phase of HIV infection, what is meant by the virologic set point
by 3-4 months viremia reduced to low levels
Degree of viremia at this point is called virologic set point
This is a predictor of disease progression
What is the HIV nadir?
CD4 nadir is lowest point of CD4 count
55 year old male NHL – starting R-CHOP
Clotted blood available
HBsAg neg
Anti-HBc pos
HBV DNA neg
Explain this serological profile
official question
HBsAg neg
Anti-HBc pos
HBV DA neg
Explain profile –
blood products - haematology patient
past infection
55 year old male NHL – starting R-CHOP
Clotted blood available
HBsAg neg
Anti-HBc pos
HBV DNA neg
What actions would you take?
official question
Rituximab high risk drug
Start tenofovir 245mg OD/ entecavir 1g OD a week before R-CHOP
Follow up HBV DNA ever 2-3 months
Monitor ALT
19 year old with lymphadenopathy and deranged LFTs
Clotted blood sample available
CMV IgM pos, IgG pos, aviditiy 0.8
EBV vca IgM pos, IgG pos, EBNA neg
Explain the serological profiles
Official question
Would want to know if patient is immunosuppressed or has had recent blood products before interpreting
CMV IgM pos, IgG pos, aviditiy 0.8
EBV vca IgM pos, IgG pos, EBNA neg
Explain profiles –
CMV –
- high avidity >0.6 indicates distant past infection
- IgM could be cross-reactive finding given EBV strongly pos
- could also be reactivation, or a re-infection, but less likely
EBV -
- consistent with recent acute primary infection
19 year old with lymphadenopathy and deranged LFTs
Clotted blood sample available
CMV IgM pos, IgG pos, aviditiy 0.8
EBV vca IgM pos, IgG pos, EBNA neg
What other tests would you do?
Official question
Rhematoid factor
HIV 1/2 Ag/Ab test - lymphadenopathy/ mononucelosis like illness
EBV/ CMV viral load
What are the CMV avidity cuttoffs?
<0.4 low
> 0.6 high
intetween - indeterminate
Mother with HIV decides to bottle feed
What drug would you give to supress lactation?
official question
Cabergoline
Cabergoline is a long-acting dopamine receptor agonist with a high affinity for D2 receptors. Inhibits prolactin secretion by the anterior pituitary
1mg on day of delivery
250 micrograms every 12 hours for 2 days after delivery
3 year old with hereditary spherocytosis. Aplastic crisis
Parvo IgM/ IgG neg
CMV IgM neg, IgG pos
EBV vca IgM pos, IgG pos, EBNA neg
RF pos
How would you interpret these results?
official question
Parvo IgM/ IgG neg
CMV IgM neg, IgG pos
EBV vca IgM pos, IgG pos, EBNA neg
RF pos
Interpretation:
- Parvo neg - but can be not detectable early infection, or immunocompromised
- CMV – past infection most likely
- EBV – RF could cause IgM reactivity. Or could be late primary, or reactivation
- note all results may be misleading if patient has received blood products
3 year old with hereditary spherocytosis. Aplastic crisis
Parvo IgM/ IgG neg
CMV IgM neg, IgG pos
EBV vca IgM pos, IgG pos, EBNA neg
RF pos
What tests would you do next?
official question
EDTA sample for:
Parvo DNA PCR
EBV DNA PCR
CMV DNA PCR
Consider follow up serology in a few weeks
Respiratory 24-plex assay
Multiple targets - viruses and bacteria
Why does our assay have both SARS-CoV-2 ORF1 and ORF8 targets?
Viruses at high risk of mutation
Minimum is to have 2 targets for SARS-CoV-2
This increases your positive predictive value when you have both targets present.
This increases your negative predictive value when both targets are absent
