NHS BT Flashcards

Question

Indirect Antiglobulin Technique

Answer 1

detects 37oC active antibodies detects IgG antibodies detects complement fixing antibodies Detects all Rh antibodies, anti-K, k, Fya, Fyb, Jka, Jkb, M (reactive at 37 deg C), S, s, Kpa, Kpb, Lua, Lub “The gold standard”

Answer 2

good for all Rh antibodies and anti-Jka, Jkb, Lea, Leb, P1 does not detect anti-Fya, -Fyb, -M, -N, -S because these blood groups are destroyed by papain treatment excellent in resolving mixtures

Answer 3

detects IgM antibodies, e.g anti-M, N, P1, Lea, Leb, H, I and ABO detects antibodies which are usually clinically insignificant (ABO antibodies excepted) detects antibodies which may give unclear IAT good for resolving mixtures

Answer 4

PEG IAT, 2-stage IAT, enzyme IAT, Capture R, albumin displacement, polybrene, 37oC saline, 31oC saline 4oC saline, NISS, LISS, BLISS, adsorptions, elutions, neutralisations………….

Answer 5

“The specificity of the antibody should only be assigned when it is reactive with at least two examples of reagent cells carrying the antigen and non reactive with two examples lacking the antigen”

Answer 6

To be certain of the identification of an antibody the panel used must give Positive results against two cells which contain the antigen Negative results against two cells which lack the antigen Exclude the presence of any other antibodies

Answer 7

Enzyme sensitive (don’t work with papain-treated cells) helps to resolve mixtures: anti-M, -N, -S, -s, -Fya, -Fyb Dosage: stronger reactions with homozygous cells (~twice as much antigen on cells) anti-Fy, -Jk (especially), MNSs, anti-c, -D (anti-D may react stronger with R2R2 cells) IgM antibodies (20oC active): anti -M,-N,-P1, -Lea,-Leb Masked antibodies Expect the expected!

Answer 8

No fit for a single specificity, auto negative ? Different strengths of reactions ? Different patterns with different techniques? Additional reactions to those in previous sample

Answer 9

``` Getting some negative results? Try to identify at least one component (there’s usually some Rh in there) Use negatives to eliminate something! Try to find more negatives (more panels) ``` Performing a patient phenotype can help (ABO, D, C, E, c, e, Cw, MNSs, P1,Lea, Leb, K, (k if K+), Kpa(Kpb if Kpa+), Fya, Fyb ,Jka, Jkb How does the phenotype help? Tells you what alloantibodies patient can form Helps you to find more panel cells May help in providing safe transfusion BUT BEWARE The transfused patient The “untransfused” patient The Positive Direct Antiglobulin Test

Answer 10

IAT Antigen – Antibody complex forms AHG added (Anti-Human Globulin) Agglutination seen

Answer 11

Can provide a full genetic type for highly prevalent antigens Simple 3 step procedure with minimal ‘hands-on’ time, giving results in under 3 hours Most technology (PCR cyclers) already present in H&I laboratories Specialised Reader

Answer 12

``` DAT positive patients Multi-transfused patients Patients with pan-reactive autoantibody that resists absorption procedures Patients with weak expression of antigen Where liquid reagents are unavailable ```

Answer 13

Extract DNA (30 mins) Prepare tests - microplate (10-30 mins) Amplify DNA – thermocyclers (c2 hours) Analysis (10 mins)

Answer 14

Samples processed in a single day 3 Samples per run, up to 8 runs a day Results available in approx 2.5 hours Good reliability with low failure rate

Answer 15

``` Newcastle and Sheffield 1056 donor samples 6 fails (0.6%) – All resolved on repeat 7 ‘indeterminate’ single types – 4 resolved on repeat ``` Similar findings in routine processing of samples

Answer 16

AIHA DAT positive Antibody combinations/SNDT Ethnic representation

Answer 17

Most useful in multi-transfused and AIHA cases Results can be obtained the same day Reproducible, Low fail rate Good concordance with serological typing results Simple to use and not labour intensive No significant wastage Direct download of results

Answer 18

Not suitable for urgent cases Not as fast as serological typing (see urgent cases above) Not suitable for rare genotypes – require sequencing ABO – simple serologically but complex genetically (not performed on this assay).

Answer 19

Genotyping improves ability to provide patients with suitable blood. Costs currently prohibit routine use for all patients. Likely greater use in future for both donors and patients ``` CE marking Direct download Reporting (Hematos / SP-ICE) Price What we do with the info; Recommendations Selection of blood ```

Answer 20

Landsteiner and Wiener (1941) found that an immune serum produced in guinea pigs immunised with blood from Rhesus monkeys reacted with red cells from 85% of the New York population. They named this new finding the ‘Rhesus factor’ 85% were ‘Rhesus’ pos, 15% were ‘Rhesus’ neg It was discovered that all Levine & Stetson’s women were ‘Rhesus’ negative and all their husbands were ‘Rhesus’ positive Following this discovery (and the subsequent confirmatory work) it was proposed that all ‘Rhesus’ negative people should be transfused ‘Rhesus’ negative blood.

Answer 21

The Rh system comprises five commonly occurring antigens. The most important one is called D The RhD gene is found on chromosome no 1 Defines Rh status in donors and patients The unlinked RhAG gene on chromosome 6 incorporates the antigen into the cell membrane D positive individuals have the RhD gene Most D negative individuals have an RhD gene deletion

Answer 22

85% RhD positive | 15% RhD negative

Answer 23

Weak D Formerly known as Du Possesses all normal D antigens, but has quantitatively less Is RhD positive as a donor, patient and an antenatal patient Cannot produce anti-D

Answer 24

Lacks part of a normal D antigen Can produce anti-D (as is missing some of the D antigen) Can cause the production of anti-D in a D negative recipient (as possess some of the D antigen) Regarded as RhD Pos as a donor RhD Neg as a recipient Antenatal patients require anti-D prophylaxis

Answer 25

``` Composed of 5 commonly occurring antigens D C c E e ``` These 5 Rh antigens are inherited as a group of 3 antigens which are inherited together C and c antigens are alleles on the RHCE gene E and e antigens are alleles on the RHCE gene There is no d antigen, most RhD negative individuals lack the D antigen (have no RHD gene)

Answer 26

Antigens Short CDe R1 1st order cDE R2 1st order cde r 1st order Cde r’ 2nd order cdE r’’ 2nd order Antigens Short cDe Ro 1st order in blacks rare in whites CDE RZ Rare CdE ry Extremely rare

Answer 27

Anti-D Anti-D is the most potent and remains a major cause of Haemolytic Disease of the Fetus and Newborn (HDFN) Produced in women as a result of sensitisation by red cells from D positive fetus May be produced in males as a result of transfusion with D positive blood.

Answer 28

Clinically significant Relatively common May cause HDFN or Haemolytic Transfusion Reaction (HTR) Often found together with anti-E

Answer 29

Anti-E ``` Clinically significant Relatively common May cause HDFN or HTR Less clinically significant than anti-c Often found together with anti-c in individuals who lack c and E antigens ```

Answer 30

``` Anti-C Clinically significant Relatively common, often seen with anti-D May cause HTR HDFN rare when on its own ```

Answer 31

Anti-e Clinically significant May cause HTR

Answer 32

Type patients for full Rh group and match the donations This is important for: All female patients under 60 yrs of age Patients who may need regular transfusions (e.g. Sickle cell disease) Patients who have already produced other antibodies (‘responders’)

Answer 33

A condition affecting fetuses and newborn infants caused by a blood group antibody in the mother attacking red cells in the infant which carry the corresponding antigen inherited from the father. The most potent form of the disease results when the mother is RhD negative and the fetus is RhD positive

Answer 34

Mother is sensitised against foreign red cell antigens on fetus Antigens which are more fully developed on fetal cells are more likely to cause sensitisation (e.g. Rh, but not ABO)

Answer 35

``` Antibodies involved include Anti-D (or D + C) Anti-Kell Anti-c Anti-E Anti-Fya Other IgG antibodies e.g –S, -Jka, other anti-Rh ABO ```

Answer 36

``` Theoretically: More IgG antibody in the maternal circulation = more crosses the placenta = more severe HDFN But… Moderate anti-D and anti-c Poor anti-K and anti-E Variable other specificities Useless ABO ```

Answer 37

Direct antiglobulin test (DAT) on cord blood. This detects IgG antibody bound to the surface of the infant’s red cells. A positive result is diagnostic of HDFN. Mild – Phototherapy under UV light Moderate – Top-up or exchange transfusion Severe – Exchange transfusion at birth or Intra-Uterine Transfusion (IUT) during pregancy

Answer 38

``` 5 days old or less, CPD red cells CMV negative Sickle cell negative Negative for any red cell antibodies Low level of anti-A and anti-B Gamma irradiated Hct 0.5 – 0.6 for ET up to 0.7 for IUT ```

Answer 39

1960’s – Sir Cyril Clarke at Liverpool Known that ABO antibodies offered some protection Prevention began in 1970 (post-natal prophylaxis) Standard dose of prophylactic anti-D (polyclonal, human derived) 500 IU up to 4mL bleed 1500 IU up to 12mL bleed FMH calculated by Kleihauer test or Flow cytometry Antenatal prophylaxis Monoclonal anti-D (not as effective)

Answer 40

``` Significant Anti-D Anti-c Anti-K Other Rh Kidd system Duffy system anti-M (37OC), -S -s ```

Answer 41

``` Not significant •anti-Lea •anti-Leb •anti-P1 •anti-H(I) •anti-N •anti-M (20oC only) ```