Transfusion transmitted infections

Question 1

What TTIs do we rely on questioning alone to minimize?

Answer 1

Malaria, CJD, Ebola

Question 2

What are some examples of immunoassays in screening for infectious disease? Nucleic acid amplification tests?

Answer 2

IA: ELISA, ChIA, EIA, western and other blots.
NAAT: PCR, TMA, NASBA

Question 3

What TTIs must we screen all units for (not optionally)?

Answer 3

HIV
HBV
HCV
HTLV
ZIKV
Syphilis

Question 4

What TTIs are selectively screened for (not in all cases)?

Answer 4

CMV
Trypanosoma cruzi
WNV (endemic areas)
Babesia (endemic areas)

Question 5

What is the consequence of many skin GPCs forming biofilms?

Answer 5

Biofilms may result in false negatives on the BacT/ALERT screening system.

Question 6

What bugs tolerate cold storage?

What bug is frequently missed on BacT/ALERT?

Answer 6

Cold: Listeria, yersinia enterocolitica.

Missed on BacT: Clostridium perfringens.

Question 7

How is testing for HIV performed?

Answer 7

MP-NAT (pools of 6-16) as a screening assay, then serology/immunoassays for confirmatory.

Question 8

What is the significance of each of the following on HBV serological testing?

HBcAb (anti-HBc)
HBsAg
HBsAb
HBV DNA

Answer 8

HBcAb (anti-HBc) - Indicates prior infection
HBsAg - Indicates presence of virus
HBsAb - Indicates immunity
HBV DNA - Indicates presence of virus

Question 9

What is occult Hep B infection (OBI)?

Answer 9

Presence of low levels of HBV DNA in liver, without having detectible DNA in serum.

Question 10

Distinguish between HTLV-1 and HTLV-2

Answer 10

HTLV-1 is geographically endemic and is associated with neoplasms. HTLV-2 is transmitted by IVDU and is not as implicated in neoplasms.

Question 11

What percentage of blood donors are seropositive for CMV?

Answer 11

40-70%

Question 12

How do seronegative units compare to untested leukoreduced units for CMV transmission

Answer 12

They are approximately equal in risk. If the seronegative unit is also leukoreduced, then it is about 2x safer.

Question 13

How is babesia tested for?

Answer 13

NAATs in endemic areas only.

Question 14

What viruses does pathogen reduction affect?

Answer 14

HIV, Zikavirus, most enveloped viruses.

Question 15

How does red blood cell pathogen reduction work?

Answer 15

Still done under INTERCEPT system, using Amustaline (S-303) and glutathione as the crosslinker.

Question 16

What are the downsides of the Mirasol system (besides it not being approved in the US)?

Answer 16

Increases anaerobic glycolysis

Increases GpIIb/IIIa-fibrinogen interactions.

Question 17

Recall some alternative methods of pathogen reduction.

Answer 17

Filtration/nanofiltration (parasites only)
Pasteurization (only for acellular plasma)
Solvent-detergents
Dry-heat and lyophilization
Methylene blue

Question 18

When is the TTI testing sample drawn relative to donation in blood donation? In stem cell harvest?

Answer 18

Blood donation: Collect at point of donation

Stem cell harvest: Collect in advance

Question 19

What happens if a serologic test is positive?

Answer 19

It should be repeated (tested in duplicate). Need two positive results to be “repeat positive”. If #1 and #2 disagree, perform in triplicate as a tiebreaker.

If a sample is repeat positive, the unit CANNOT be used for allo transfusion.

Question 20

What happens if a NAAT is positive?

Answer 20

If a minipool was positive, split into individual units. Any positive result on an ID-NAAT effectively kills the unit.

Question 21

For what organisms is NAAT done in individual pools up front?

Answer 21

WNV, in specific areas. MPs can dilute the RNA too much…

Zikavirus too?

Question 22

When are look-backs required to occur?

Answer 22

By law, only when HIV/HCV testing is positive (RR serology or ID-NAAT), but usually for all infectious agents. Must retrieve other products within 3d or 1wk.

Question 23

When do autologous units needs to undergo IDM testing?

Answer 23

When they are shipped between facilities.

Question 24

What ID testing are tissues and stem cells subjected to?

Answer 24

Totally depends on the organ, but all should be tested for HIV, HBV, HCV, and syphilis. WBC-rich units should be tested for CMV & HTLV, lung for WNV, and do STI testing where appropriate…

Question 25

What contributors explain why our IDM transmission rate is not 0%?

Answer 25

Emerging infections Quarantine failure Window periods Untestable infections

Question 26

How can you predict the probability of infectious transmission of a TTI?

Answer 26

Multiply the length of the window period by the incidence in the donor population.

Question 27

What is the window period and risk of transmission of HIV?

Answer 27

9d window period | 1:1.5 million risk.

Question 28

What is included in the HBV screen?

Answer 28

HBsAg (anti-HBs) HBV DNA Total HBcAg (total IgM and IgG anti-HBc)

Question 29

What is the window period and risk of transmission of HBV?

Answer 29

18-38d window period | 1:1 million risk.

Question 30

What is included in the HCV screen?

Answer 30

HCV RNA | Serology (anti-HCV IgG only)

Question 31

What is the window period and risk of transmission of HCV?

Answer 31

7. 4d window period | 1: 1.1 million risk.

Question 32

How can HTLV be transmitted from person-to-person?

Answer 32

Blood (such as in IVDU and transfusion), sex, and breastfeeding.

Question 33

How is testing for HTLV performed?

Answer 33

Serology only (note: Cannot distinguish -I from -II). Confirm with a western blot (not NAAT).

Question 34

How is syphilis testing performed

Answer 34

Nonspecific tests (eg. VDRL/RPR): If positive, follow up with a specific test. Specific tests: If positive, one-time reactive is enough (do not need repeat reactive).

Question 35

What techniques reduce the risk of septic transfusion reaction?

Answer 35

Disinfection of phlebotomy site Diversion of first 10-40mL Detection (culturing)

Question 36

How can transfusion-transmitted arboviruses be navigated?

Answer 36

eg. Chikungunya, dengue, Zika | If no testing exists, rely on history only. Pathogen reduction should eliminate most arboviruses...

Question 37

How is Trypanosoma Cruzi tested for?

Answer 37

One-time test per donor by FDA recs | Screening EIA, confirmatory ChLIA.

Question 38

How is babesia tested for?

Answer 38

Can diagnose by manual smear review, but there are new immunofluorescence and ID-NAT assays.

Question 39

Distinguish CJD and vCJD with regards to transfusion transmission.

Answer 39

CJD can be transmitted by tissues other than blood products. Only vCJD has been implicated in transfusion-transmission (3-5 cases ever).

Question 40

How is commercial plasma treated for pathogen reduction? How effective is this?

Answer 40

Prolonged heat or solvent/detergent, maybe filtration, fractionation, and other methods. Parvovirus can resist and DNA is detectible in nearly all units, but at such low levels they are not thought to post an infectious risk.

Question 41

What is Octaplas?

Answer 41

SD and methylene blue treated plasma.

Question 42

What are the major downsides to pathogen reduced products?

Answer 42

Increased cost Decreased cellular yield Possibility for neoepitope formation

Question 43

What testing must be done on all transplanted solid organs?

Answer 43

HIV, HBV, HCV, Syphilis CMV, EBV If deceased donor: Toxoplasma, bacterial cultures If living donor: TB, other endemic disease markers.