ag phenotyping in chronic transfusion recipients

[transfusionpgi]

what is the right time for antigen phenotyping after a blood transfusion, especially in chronically transfused recipients, like those with tx dependent thalassemia, CRF on hemodialysis, etc.

(We know that type of agglutination pattern in tube or gel will give a clue to ****- or heterogenity of rbc population, eg. mixed field, weaker agg, etc. Still what is the "IDEAL' time interval after last tx?)

[Yanxia]

I think this depend on how many blood have been transfused. And gene detect if a good approach.

[David Saikin]

If you can wait 3 months p transfusion, that would be ideal. Alternately, you can try typing retics (using top 5mm from spun capillary tubes).

[Malcolm Needs ☆]

I agree with David and Shily.

David for the 3 months for serological typing, and Shily for the suggestion that you use a genetic approach.

Certainly, these days we use a genetic approach in the NHSBT if we want to know the patient's actual type, and this can be done immediately after a transfusion.

[transfusionpgi]

I agree with David and Shily.

David for the 3 months for serological typing, and Shily for the suggestion that you use a genetic approach.

Certainly, these days we use a genetic approach in the NHSBT if we want to know the patient's actual type, and this can be done immediately after a transfusion.

We are a small facilityand don't have gene typing facility around also. Can anybody please share the SOP for retic typing?

Thanks in anticipation.

[David Saikin]

While I do not have a procedure, you can take spun whole blood (EDTA) and put red cells in capillary tubes (10?). Centrifuge in a microhct centrifuge. Break off the top 3-5mm of spun packed cells. These should be rich in retics and may be used for ag typing. If anyone else has a formal procedure, feel free to jump in and provide it.

[Yanxia]

I remember have seen it in 15 edition of AABB technical mannual, but I am sorry it is not on my hands.

[jwho]

My lab uses capillary tubes from a company called safetec out of PA. They have a plunger that goes along with the capillary tubes so it's safer, OSHA wise. We wash the EDTA tube and fill the capillary tubes. Spin them in a centrifuge and express the retics. If you look at the tube you can see a difference in blood.

[TimOz]

Here is the method.

I have not used this myself but have seen it done at a lab in Taiwan where they call the "Neocyte seperation Technique" and use it routinely with some success. There is no substitute for a blood sample before the first transfusion - except perhaps for molecular methods if you have access to them.

Procedure

1. Wash the red cells three times in saline. For the last wash, centrifuge them at 900 to 1000 g for 5 to 15 minutes. Remove as much of the supernatant fluid as possible without disturbing the buffy coat. Mix thoroughly.

2. Fill 10 microhematocrit tubes to the 60-mm mark with well-mixed washed red cells.

3. Seal the ends of the tubes by heat or with sealant.

4. Centrifuge all tubes in a microhematocrit centrifuge for 15 minutes.

5. Cut the microhematocrit tubes 5 mm below the top of the column of red cells. This 5-mm segment con-tains the least dense, hence youngest, circulating red cells.

6. Place the cut microhematocrit tubes into larger test tubes (10 or 12 × 75mm), add saline, and mix well to flush the red cells from the microhematocrit tubes. Then, either a) centrifuge them at 1000 × g for 1 minute and remove the empty hematocrit tubes or transfer the saline suspended red cells to a clean test

tube.

7. Wash the separated red cells three times in saline before resuspending them to 2% to 5% in saline for testing.

Notes

1. Separation is better if 3 or more days have elapsed since transfusion than

if the sample has been obtained shortly after transfusion.

2. The red cells should be mixed continuously while the microhematocrit tubes are being filled.

3. Separation techniques are only effective if the patient is producing normal or above-normal numbers of reticulocytes. This method will be ineffective in patients with inadequate reticulocyte production.

4. Some red cell antigens may not be as strongly expressed on reticulocytes as on older cells. Particular attention should be given to determinations of the E, e, c, Fya, Jka, and Ge antigens.