Haematology (Transfusion microbiology)

Question 1

What viruses are tested for in donor blood?

Answer 1

• HBV
• HCV
• HTLV-1
• HIV
• CMV

Question 2

What are the limitations of testing?

Answer 2

• Infections can occur even when there are no ‘test failures’ - can only test for what we know about
• ‘Window period’ - time between donor acquisition and when the test would be able to detect it
• Test would be negative but donor could still transmit infections via blood

Question 3

What are some further safety measures?

Answer 3

1) Donor safety
- very small individuals, individuals with dangerous jobs etc would not be allowed to donate for the safety of the donor

2) Donor questionnaire
- Trying to identify high risk individuals due to ‘lifestyle risks’ e.g if donor has injected drugs, traveled to area of the world with particular pathogens

3) Not paid - encourages people to tell the truth
4) People transfused since 1980 not allowed to donate due to vCJD risk

Question 4

What are the risks of these viruses being transmitted during transfusion in the UK? HBV, HBV and HIV

Answer 4

HBV - 1 in 3 million
HCV - 1 in 28 million
HIV - 1 in 6.5 million

Question 5

What is the ‘window period of HBV, HCV and HIV?

Answer 5

2 weeks
12 days
22 days

Question 6

How many reported cases of HBV transmission were there in 2014/15

Answer 6

1 case

Question 7

When was HEV introduced to donor screening?

Answer 7

1st May 2016

Question 8

When are bacterial transmission usually seen?

Answer 8

One of the earliest recognizable complications of transfusion

Question 9

Are bacterial infections tested for in RBC donors?

Answer 9

No

Question 10

How are bacterial transmissions controlled?

Answer 10

1) First 20-30ml of blood is removed for testing - contains skin plug that will likely be highly bacterial

2) Donor selection
- healthy donors only, not those with evident infection

3) Cleansing of donors arm at donation
4) Aseptic techniques
5) Storage of blood at 4oC limits bacterial replication (shelf life 5 weeks)

Question 11

What is SHOT?

Answer 11

Serioud hazards of transfusion - publish annual reports of amount of transfusion infections

Question 12

The UK SHOT report showns how many cases of bacterial infection transmitted to patients in the last 18 years before 2009?

Answer 12

43 cases, 11 deaths

Question 13

What were these 43 cases a result of?

Answer 13

Causative products:
RBCs x7
Pooled platelets x20
Apheresed platelet x16

Question 14

Why has there been no incidences of transmitted bacterial infections since 2009?

Answer 14

Bacterial screening of platelets was started

Question 15

How is Fresh Frozen Plasma and Cryoprecipitate stored?What is the consequence of this on bacterial growth?

Answer 15

Stored at -30oC for up to 1 year, bacteria cannot grow

Question 16

How may some pathogens contaminate FFP and cryoprecipitate?

Answer 16

Pathogens in waterbaths used to thaw units

Question 17

What is the labs role in detecting bacteria infections?

Answer 17

1) Inspecting appearance of blood
2) Initiate recall if infection is suspected
3) High levels of cleanliness in areas where products are stored
4) Meticulous records

Question 18

How are patients with malaria prevented from donating?

Answer 18

1) Questions
- asking about travel to areas of South Americal where T. cruzi is endemic

• Malaria antibody test for donors who have had malaria at one point
• T. cruzi antibody test available

Question 19

How are people tested for sickle cell disease?

Answer 19

Sickle testing carried out to rule out heterozygous HbS individuals