ABORh and screening

Hello. For patients that may require a transfusion or require a pre-admission testing, ABORh grouping and antibody screening is done.

For ABORh grouping:

This step if done manually, comprises of the following reagents : anti-A, anti-B, anti-A,B, anti-D, A cells, B cells and O cells. These reagents are already added into the glass tubes by the staff before. This is because we receive a lot of orders everyday we cant simply wait for the specimens to arrive before dripping the reagents. After receiving the EDTA specimen, we'll centrifuge them.

Since the plasma layer is on top, we'll drip 2 drops of serum into each of the reverse grouping tubes, i.e. the A, B and O cells tube. The purpose of this step is to not disrupt the red cells below. Then, we'll pick up some red cell, dilute it in saline and add 1 drop of the 3-5% RBC suspension into each of the 4 forward grouping tubes, i.e. anti-A........ After this step is done, we'll give the 7 tubes a good shake and mix and then centrifuge them at 3,000rpm for 15seconds. Then, we gently agitate the cell button and record the results.

Procedures:

1) Spin specimen in a table top centrifuge at 3,500rpm for 7minutes.
2)Clearly label 7 glass tubes for forward (anti-A, anti-B, anti-A,B) and reverse grouping(A, B, O cells)
3)Into each corresponding tube, add 1 drop of the correct reagent.
4)Using a clean pipette, add 2 drops of test serum into each of the 3 reverse grouping tube.
5)Using the same pipette, prepare a 3-5% red cell suspension of the test cells in 0.9% saline.
6)Add 1 drop of the 3-5% suspension of cells into each of the 3 tubes containing anti-sera.
7)Give them a good mix.
8)Immediately spin them at 3000rpm for 15seconds.
9)Gently agitate and record results

If you don't mix the reagent and test cells/serum before centrifugation, you may not be able to get the correct results. So, it's very important we give the tubes a good mix before centrifugation, especially the reverse grouping tubes.

The next step we do will be antibody screening. There are 2 ways to screen for antibodies, the first will be using the tube method and the second will be using the microtyping Gel cards . I found that the Microtyping Gel cards give a more accurate results. There was this once, i took a specimen which had a 2+ reading using the machine. Then i tried to do manual screening, i ended up getting a negative result. Then i approached one of the staff(tp graduate). She repeated the manual testing with me, results obtained was still negative. Then she did the gel card method again. Tadum! 2+. Moral of the story: Gel Card > Tube. Anyway, the tube method is no longer in use, at least over here.

For gel card method, here is the procedures we take:

1)Identify the appropriate microtubes of the ID-Card"LISS/Coombs"
2)Remove the aluminium foil from as many microtubes as needed. 3)Pipette 50µl of SPO cells I, II and III into the appropriate microtubes marked with the corresponding test cells.
4) Add 25µl of the patient's plasma to each microtubes. 5)Incubate the ID-Card for 15minutes at 37 degrees in the ID incubator. 6)Centrifuge the ID card for 10 minutes in the ID centrifuge 7)Grade and record the results in the appropriate worksheet

The SPO cells are panel cells that contains some antigens, each of the 3 panel cell suspension contains different combinations of a some antigens. These antigens are blood group antigens like C, C, S, Mia etc...

So after test serum is added in, the cards are incubated at 37 deg for 15minutes. This allows agglutination to occur. If agglutination occurs, the agglutinated cells cannot pass through the gel while the nonagglutinated cells can pass through the gel.

A strong positive is seen as a line on the surface while weaker positives are distributed through the gel. To have an idea of how it looks like, click on the 2 links below.

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgm0t3RmarwNG2vWfNvlkLg7Tzlhp7nkONEbqjSOeSSamrxZXsreQktRBkOpjjM5hRljWvnbIkHcVokqxHcgeE8GnU6au9dsllIMMYkzknmxKlXnyvBntC_dVIURSG3uRHC6B68i2Sf7np_/s320/230720071167.jpg

This link shows the card that we use here. See the green part of the label, there are 3 lines, normally we'll write in I, II and III. As for the white portion, we'll write in the patient's ID. A patient only requires 3 microtubes, so 1 Gel card can be used for 2 patients.

http://www.cardinalhealth.com/us/en/distributedproducts/images/S/SPMTS4024.jpg

This link shows 6 microtubes, the reactions are 4+. 3+, 2+, 1+, neg and neg respectively.

Here are the reasons why Microtyping Card Gel does better than the tube method. For the ID-Card gel system, labour intensive washing procedures are eliminated, this is because the panel cells are added to the microtubes before the plasma and serum is, thus, creates a barrier over the gel suspension. This step can prevent neutralization of AHG (present in card gel) by Serum IgG protein.

This antibody screening result is valid up to 14 days unless the patient has been recently transfused or is pregnant within the past 3 months. For a patient who is has received a transusion or is pregnant within the last 3 months, antibody detection must be performed on a specimen obtained within 3 days of the next scheduled transfusion. This is because these patient may have been sensitized and they may be producing new antibody that was not previously identified.

If the samples tested positive for antibody screening (a positive in any of the 3 microtubes) but has no known antibody on record, we'll repeat the screening and then sent the specimen down to Blood Services Group (BSG), aka CTM for antibody identification.

Yanhong / TG01 / 0703979E