Transfusion transmitted infections Flashcards
What TTIs do we rely on questioning alone to minimize?
Malaria, CJD, Ebola
What are some examples of immunoassays in screening for infectious disease? Nucleic acid amplification tests?
IA: ELISA, ChIA, EIA, western and other blots.
NAAT: PCR, TMA, NASBA
What TTIs must we screen all units for (not optionally)?
HIV HBV HCV HTLV ZIKV Syphilis
What TTIs are selectively screened for (not in all cases)?
CMV
Trypanosoma cruzi
WNV (endemic areas)
Babesia (endemic areas)
What is the consequence of many skin GPCs forming biofilms?
Biofilms may result in false negatives on the BacT/ALERT screening system.
What bugs tolerate cold storage?
What bug is frequently missed on BacT/ALERT?
Cold: Listeria, yersinia enterocolitica.
Missed on BacT: Clostridium perfringens.
How is testing for HIV performed?
MP-NAT (pools of 6-16) as a screening assay, then serology/immunoassays for confirmatory.
What is the significance of each of the following on HBV serological testing?
HBcAb (anti-HBc)
HBsAg
HBsAb
HBV DNA
HBcAb (anti-HBc) - Indicates prior infection
HBsAg - Indicates presence of virus
HBsAb - Indicates immunity
HBV DNA - Indicates presence of virus
What is occult Hep B infection (OBI)?
Presence of low levels of HBV DNA in liver, without having detectible DNA in serum.
Distinguish between HTLV-1 and HTLV-2
HTLV-1 is geographically endemic and is associated with neoplasms. HTLV-2 is transmitted by IVDU and is not as implicated in neoplasms.
What percentage of blood donors are seropositive for CMV?
40-70%
How do seronegative units compare to untested leukoreduced units for CMV transmission
They are approximately equal in risk. If the seronegative unit is also leukoreduced, then it is about 2x safer.
How is babesia tested for?
NAATs in endemic areas only.
What viruses does pathogen reduction affect?
HIV, Zikavirus, most enveloped viruses.
How does red blood cell pathogen reduction work?
Still done under INTERCEPT system, using Amustaline (S-303) and glutathione as the crosslinker.
What are the downsides of the Mirasol system (besides it not being approved in the US)?
Increases anaerobic glycolysis
Increases GpIIb/IIIa-fibrinogen interactions.
Recall some alternative methods of pathogen reduction.
Filtration/nanofiltration (parasites only)
Pasteurization (only for acellular plasma)
Solvent-detergents
Dry-heat and lyophilization
Methylene blue
When is the TTI testing sample drawn relative to donation in blood donation? In stem cell harvest?
Blood donation: Collect at point of donation
Stem cell harvest: Collect in advance
What happens if a serologic test is positive?
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.
What happens if a NAAT is positive?
If a minipool was positive, split into individual units. Any positive result on an ID-NAAT effectively kills the unit.
For what organisms is NAAT done in individual pools up front?
WNV, in specific areas. MPs can dilute the RNA too much…
Zikavirus too?
When are look-backs required to occur?
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.
When do autologous units needs to undergo IDM testing?
When they are shipped between facilities.
What ID testing are tissues and stem cells subjected to?
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…
What contributors explain why our IDM transmission rate is not 0%?
Emerging infections
Quarantine failure
Window periods
Untestable infections
How can you predict the probability of infectious transmission of a TTI?
Multiply the length of the window period by the incidence in the donor population.
What is the window period and risk of transmission of HIV?
9d window period
1:1.5 million risk.
What is included in the HBV screen?
HBsAg (anti-HBs)
HBV DNA
Total HBcAg (total IgM and IgG anti-HBc)
What is the window period and risk of transmission of HBV?
18-38d window period
1:1 million risk.
What is included in the HCV screen?
HCV RNA
Serology (anti-HCV IgG only)
What is the window period and risk of transmission of HCV?
- 4d window period
1: 1.1 million risk.
How can HTLV be transmitted from person-to-person?
Blood (such as in IVDU and transfusion), sex, and breastfeeding.
How is testing for HTLV performed?
Serology only (note: Cannot distinguish -I from -II). Confirm with a western blot (not NAAT).
How is syphilis testing performed
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).
What techniques reduce the risk of septic transfusion reaction?
Disinfection of phlebotomy site
Diversion of first 10-40mL
Detection (culturing)
How can transfusion-transmitted arboviruses be navigated?
eg. Chikungunya, dengue, Zika
If no testing exists, rely on history only. Pathogen reduction should eliminate most arboviruses…
How is Trypanosoma Cruzi tested for?
One-time test per donor by FDA recs
Screening EIA, confirmatory ChLIA.
How is babesia tested for?
Can diagnose by manual smear review, but there are new immunofluorescence and ID-NAT assays.
Distinguish CJD and vCJD with regards to transfusion transmission.
CJD can be transmitted by tissues other than blood products. Only vCJD has been implicated in transfusion-transmission (3-5 cases ever).
How is commercial plasma treated for pathogen reduction? How effective is this?
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.
What is Octaplas?
SD and methylene blue treated plasma.
What are the major downsides to pathogen reduced products?
Increased cost
Decreased cellular yield
Possibility for neoepitope formation
What testing must be done on all transplanted solid organs?
HIV, HBV, HCV, Syphilis
CMV, EBV
If deceased donor: Toxoplasma, bacterial cultures
If living donor: TB, other endemic disease markers.
