5. Pretransfusion testing Flashcards
6 crucial steps for safe transfusion
- ID of patient and donor with appropriate sample collection
- Testing of donor sample
- Testing of patient sample and patient history review
- Selection of appropriate units
- Crossmatch
- Re-identification of patient before infusion
circle of safe transfusion
Patient wristband → BB sample → crossmatched units → transfusion request record → patient wristband
sample condition requirements (5)
- labelled correctly (2 identifiers); date; phlebotomist’s ID
- sufficient quantity
- minimal hemolysis
- appropriate site (not above IV)
- indelible ink used
records kept indefinitely
any difficulty in typing
clinically significant Abs
I, II and III screening cells are type — and have at least one cell…
O
homozygous for all clinically significant Abs
selection of appropriate units
- type-specific preferred
- use short-dated
- conserve O for O patients
preferred form of XM
EXM
You can stop XM after negative IS or EXM if…
negative ABS
no hx of significant Ab
serves as final check for ABO/Rh compatibility
XM
major XM
pt plasma + donor cells
minor XM
donor plasma + pt cells
often to blame for XM incompatibility
autoAB
potential reasons for XM incompatibility (5)
- autoAb
- alloAb
- error in unit selection/typing
- excessive protein in pt serum
- contaminants in test system
in emergencies, O= is given to….
females
males < 12 yo
in emergencies, O+ is given to…
males > 12 yo
Rh= patients that may receive Rh+ blood with pathologist approval
adult males
females > 50yo
included on blood transfusion request form (4)
Pt 2 identifiers
Product requested
Physician
Transporter to patient care area
included on label on issued units (3)
ID of intended recipient
Statement of compatibility
Unit or pool number
read back includes… (5)
Intended recipient’s 2 IDs and ABO/Rh
Donor unit number and ABO/Rh
XM interpretation, if required
Special requirements
Date and time of issue (expiration)
type for patient w/o hx of type
checktype
reflex ABS procedures
ABS panel
antigen typing
2-unit XM (if sample labelled for transfusion)
miniature automated tube tests
microtiter plate
solid phase measures…
adherence of analyte to solid phase
SPRCA
solid phase red cell adherence
in solid phase, patient plasma is incubated with —— on a tray of wells containing….
LISS
bound known antigen
added after incubation and washing of solid phase plate
why?
indicator cells with anti-IgG
allow visualization of Ab from plasma bound to antigen in solid phase
solid phase plate is incubated at —– for —– mins
37°
30 mins
positive solid phase reaction
indicator cells adhere to wells
negative solid phase reaction
cell button; no adherence of indicator cells
tests performed in solid phase in a well that is activated only
DAT
weak D
XM
how is solid phase for XM, DAT, and weak-D different?
cells adhere to wall
pt plasma is added for XM
anti-D is added for weak D
indicator cells are added for DAT
gel technology principle
antigen is suspended in gel medium
red cell agglutinates stay near top; nonagglutinated red cells pass through to the bottom
how are gel IAT and gel DAT different?
IAT: IgG is in the gel
DAT: anti-IgG is in the gel (no C3)
advantages of alternative tech (7)
- Standardized technique – consistent, reproducible and stable end points
- Less subjectivity
- Stability of test results
- Decreased sample volume
- Enhanced or equivalent sensitivity
- Automation is available
- Larger batches (ie Red Cross)
disadvantages of alternative tech (7)
- Cost (equipment, training, reagents, etc)
- Some methods do not allow detection of both IgM and IgG, or cannot distinguish between them (ie Gel)
- Gel has difficulty with rouleaux, fibrin — false positives
- May not provide information on the phase and temperature of reactivity of antibodies
- Increased sensitivity my cause insignificant antibodies to be detected
- Solid phase requires a wash step
- Long TAT, especially with gel
