Blood Banking

Hi, Liyana here :)

During my first week I was appointed to the blood banking section.

Once sample is received (in an EDTA tube), it needs to be checked for clotting, if there is clotting, the sample needs to be rejected. If no clotting is observed, the sample will be centrifuged to seperate the RBC portion from the plasma.

The lab uses an automated ABO/Rh typing and Ab screening. The analyzer is known as AUTOVUE Innova which uses the same principle as gel card technique. The sample would be loaded onto the analyzer. The analyzer uses a cassette for ABO/Rh typing, the cassette consists of forward and reverse grouping. The cassette has 6 columns consisting of:

Forward grouping (reagents are readily present in column):
1. anti-A
2. anti-B
3. anti-D

Reverse grouping (reagents will be added to the column):
1. A cells
2. B cells

(note: It does not use O cells)

The last coloumn is used as a control, whereby the probe would add patient's serum and RBC (initially diluted in saline).

The probe would initially suck up the plasma (this is done first to prevent disruption of the sepration between plasma and RBC) and add it to the columns containing A cells, B cells and the control. Subsequently, it would suck up the RBC and dilute it in saline before it is added to columns consisting of anti-A, anti-B, anti-D and control.

The cassette would then be transported to the centrifuge (located within the analyzer as well). It would undergo two type of centrifugation, low speed and high speed. The purpose of low speed is to allow the cells to intereact with the reagents. The high speed is to seperate the agglutinated cells from the non-agglutinated cells. The agglutinated cells would be large and will not be able to migrate to the bottom of the column, settles at the top. However, non-agglutinated cells are small enough to seep through the beads in the column and settle to the bottom.

As for Ab screening, the cassette consists of AHG for detection of IgG Ab. BLISS will be added to each column to lower zeta potential and enhance interaction between RBCs and Abs . Then, S1, S2 and S3 cells would be added to respective columns followed by plasma to each column (plasma is added later to prevent neutralization of AHG). Therefore, Ab screening only makes use of three columns though there are six columns in one cassette (the cassettes can run two different samples). Unlike, ABO/Rh typing, the cassette needs to be incubated for ten minutes before it undergoes centrifugation (both low and high speed). Interpretation of results is smilar to that of ABO/Rh typing.

The analyzer would read the cassettes and determine the patients ABO/Rh group and detect if there are clinically significant Ab present. However, Ab screening result would only appear as positive or negative, it would not be able to identify the Ab if result is positive.

Subsequently, results would be checked against the patient's history. If there are discrepancies or no history of the patient is found, the test would then be conducted again manually for rechecking. The lab uses tube method for ABO/Rh typing (similar to practicals done in school). However, it uses the gel card technique for Ab screening. A same cassette for Ab screening used by the analyzer is used for this method too. The steps for Ab screening using gel card technique are as follows:

1. S1, S2 and S3 cells are added to the three columns respectively.
2. Plasma is added to each column.
3. Incubation
4. Centrifugation
5. Read results; grade accordingly i.e.: 4+, 3+, 2+, 1+, 0

If a crossmatch needs to be conducted, the patient's Ab screening results will determine the type of crossmatch. If Ab screening result is negative, an abbreviated crossmatch is conducted whereby donor's RBC (diluted in saline) is reacted with patient's plasma. However, if Ab screening is positive, a full crossmatch (similar to practicals done in school) needs to be conducted whereby the three phases, i.e: saline, LISS and AHG, needs to be conducted using donor's RBC (diluted in saline) and patient's serum. In addition, if the results is negative in the AHG phase, Coomb's reagent needs to be added by acting as a control to ensure that the AHG is not neutralized by unbound Abs.

Liyana
0703827F
TG01