Transfusion Transmitted Disease Flashcards
Attempts to prevent diseases in donated blood
1972 can only accept blood from volunteer (non paid) donors. DHQ and information about high risk lifestyles
Required infectious disease testing (8)
HIV, HCV, HBC, HTLV, WNV, Syphillus, Zika and Chaga’s (Bacteria is tested for as well) (Babesia test may be coming out soon)
HIV required testing
anti-HIV (IGM and IGG) or anti-HIV+O (IgM +IgG)(either ELISA or ChIA) and HIV NAT (RNA) (PCR or TMA)
HCV testing
anti-HCV (IgG) and HCV NAT (RNA)
HBV testing
HbsAg, anti-HBc (IgM and IgG) and HBV NAT (DNA)
HTLV
(both I and II) anti-HTLV I /II(IgG)
Syphillis
Trepanmeal antibody (IgG and IgM) and/or non treponemal RPR testing
WNV
WNV NAT (RNA)
Zika
Zika Virus NAT (RNA)
Chaga’s disease
anti-Trypanosoma cruzii (IgG)
DHQ
tries to screen donors for things we do test for with questions (HIV/HCV etc) Tries to screen donors for things we don’t test for (malaria, CJD, vCJD) and does not have any questions for somethings we DO test for (WNV, Zika, HTLV)
Autologous blood collection must be completed…
72 hours prior to procedure
ELISA 3 different types
enzyme linked immunosorbent assay (Direct, Indirect and Sandwich or capture assay)
Direct EIA
(or elisa) is an antigen of interest immobilized and bound to the well and a target antibody with tag is added to the solution
ELISA sensitivity and specificity
exteremely sensitive, not a lot of false negatives, however not as specific could have high number of false positives
Chia
chemilluminescent immunoassays, variation of colorimetric ELISA test, substrate causes flourescence that reacts with light of certain wavelength
What is the antibody with attached signal molecule that binds in an ELISA assay
conjugate antibody
What causes an enzymatic color change in ELIZA
substrate
Indirect EIA
antigen is immobilized and bound to well/plate, antibody of patient (if present) then binds to antigen,
sandwich EIA
Antibody (capture antibody) is bound to well, antigen in the patient binds to these antibody (if present) second conjugate antibody with tag binds to first antibody, chemical change causes colorimetric change for identification
Conjugate
conjugated to enzyme that causes indicative change with addition of substrate, antibody that binds either Fc portion of target antibody, or to target antigen
If serologic testing is positive
Donor must be deferred, however there is a large percentage of false positives, donor can potentially be eligible for re-entry later
Confirmatory Testing
FDA mandates that supplemental or confirmatory testing if available
If initial sample test is reactive:
repeat the sample in duplicate, if either of the repeated samples are positive, unit must be discarded and supplemental testing performed if available. IF both repeated samples are negative, unit can be released.
Substrate
added at the very end in order to stimulate the enzyme into a colorimetric or fluorescent change for detection
NAT
Nucleic acid test, became licensed in 2002 this is highly specific testing, detects either RNA or DNA through amplification of specific nucleotide sequence
MP
minipool (about 16 donors) pool the blood together to do NAT testing, can rule out all at once if negative, if positive need to determine which one is positive by repeating NAT individually
Advantage of NAT
reduces the ‘window period’ (HIV, HCV, HBV) can detect before antibodies are able to be made (WNV, Zika)
HIV
Human immunodeficiency virus, Single stranded RNA, two main types HIV-1 and HIV-2 has several groups (M, N, O and P-most infections worldwide are M ) HIV-2 is less infectious, typically associated west africa. Transmission is 25% infectious- paternal, sexual, blood exposure. Infects CD4 helper T cells
TMA
transcription mediated amplification
HIV deferal
permanent deferral if antibody and HIV-1 RNA is positive. If serology is negative but HIV-1 RNA is positive-indefinte referral until further testing is done
HIV supplemental testing to anti-HIV 1/2
hiv-1 rna can be used as supplemental testing (if negative can use HIV-1 western blot or HIV-1 IFA)
IFA
indirect immunoflourecence assay **
With NAT the window for HIV is approximately how many days?
9 days
HBV
Douple straned DNA hepadnavirus, this virus is much more hardy than HIV and can live on surfaces for weeks . There are two serological markers for this HbsAf and antibody to hepatitis B core antigen. with three markers, result outcome can be complex
Hepatitis B surface antigen
detection using either EIA or ChIA, if positve sample repeated in duplicate, if supplemental test result is positive donor is permanently deferred, if not confirmed with supplemental test donor can be reentered in 56 days (8 weeks)
Positive HbsAg negative supplemental tests
reentry of donor after 56 days/8 weeks
Supplemental testin for HbsAG
HBV-NAT can be used as supplemental i negative or not already being used as supplemental