Percent Recovery

[n.peters]

I was wondering how others do their percent recovery on whole blood and apheresis red cells. Do you do it by weight or mass? Also, for anybody that has the Haemonetics MCS+ LN 8150, if you do the 832F kit how are you calculating red cell recovery? Thanks

[heathervaught]

We started using weight-only RBC recovery whenever possible over the last 5 years. We started out with one filter type, and validated that any discrepancies betwen the hct method and the weight-only method was due to the variation in the analyzer. When validating a new filter (including the filter attached to the 832F kit), we prove that the filter does not preferrentially hold-up RBCs or plasma (statistically that the pre-hct = post-hct within the tolerance of the analyzer), then make the statement in the validation summary that the pre and post weights can be used to calculate RBC recovery.

[ar_confederate]

We also perform the calculation using the weight. It's quick, easy and all of the inspectors have accepted it without a problem.

[fmatheu]

What formula did you use when you used HCT. I am going to start leukoreducing and I want to do it with HCT first and compare it to weigh.

[heathervaught]

(Post hct x Post wt) / (Pre hct x pre wt)

Remember that you are not trying to prove that you get the SAME results with a weight-only method, but that you are getting a MORE ACCURATE result.

[fmatheu]

Here is the formula we use for percent recovery for frozen red cells. I could use the same formula, but I do not want to use HCT for LR. I want to know where the .0693 comes from in my density formula. It was established by the Freezing Protocol, FDA does not have a problem with it. I am training someone and he asked where the number comes from. I can't explain it. Do you know?

Pre-GlycerolizationDeglycerolizationWeight266371Hematocrit7549Density1.0569751.038957RBC Concentration251.66357.09RBC Volume188.75174.97Percent Recovery92.70% Use HCT in decimal format. Use 75% for the pre-glycerolization HCT.Density (calculation = (0.0693 * HCT)+1.005)RBC Concentration = (Net Weight/Density)RBC Volume = (RBC Concentration * HCT)Percent Recovery = (Deglycerolization Volume/Preglycerolization Volume)

[jkdmendoza]

(Post hct x Post wt) / (Pre hct x pre wt)

Remember that you are not trying to prove that you get the SAME results with a weight-only method, but that you are getting a MORE ACCURATE result.

pre wt , is the weight of the whole blood?

[heathervaught]

If you are filtering whole blood, then yes. But remember to also use whole blood as the weight for the post weight as well.

[jkdmendoza]

i really need your help we are using this formula since i came here in blood bank to get the percent recovery:

final hct x vol of PRBC X 100

orig. hct x vol of prbc

i always get more that 100% for my CPDA1 blood bag please correct me if am worng in doing this procedure

we are using manual plasma extractor. After centifuging the blood bag at high speed (CPDA1-because we are currently using double bag) we are leaving at least 1/2 to 1 inch plasma for CPDA1 bag. mix well until the prbc are homogenous after which releasing adequate amount of prbc into the segment, seal, cut and measure the hematocrit in our CellDyn 3700. the measurement of post hct is greater than the pre hct. these are my datas:

final hct = 51.3 %

original hct. = 40 %

volume of whole blood = 446 mL

volume of PRBC = 212 mL

using the formula we have i always get more than 100% but the percent recovery of CPDA1 blood bags should only have less than 80%.

I hope and wish that you can help me with this problem.

Thank you very much.

[heathervaught]

jkdmendoza,

You do not need to calculate RBC recoveryf or the procedure you described above. You have taken whole blood, spun in a centrifuge, then removed plasma. Except for a miniscule number of RBCs that are lost in the plasma, you have retained virtually 100% of the initial RBC content. The "<80%" target for CPDA-1 RBCs referrs to the hematocrit of the final product.

If you then take the CPDA-1 RBC component and pass through a leukorerduction filter, then you would calculate the RBC recovery using the formula you described.

Edited June 20, 2010 by heathervaught
typimg with one hand yields a few spelling errors!

[jkdmendoza]

thank you very much for your reply, now i understand the procedure.