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C/T Ratio


kirkaw

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Most of my docs/services are well below a CT of 2. In the past I have seen the neurosurgeons have a significantly higher CT than is usually accepted. The feelings from all the docs on my utilization committee was that if they are going to cut into someone's brain, they can have any CT ratio and it will be acceptable.

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Thanks for the input. We do not have a transfustion committee (I know, GASP!) and our cardiothoracic surgeons are averaging a C/T ratio of 3.3! I have been watching this for 4 months now and before I call attention to it, I wondered if anyone else let's this slide. I know 20+ years ago, when I started in blood banking, we set up 8 units of blood for every open heart surgery, but now it's only 2 and most of those come back. Also, I believe or protocol heart surgeries was implemented in 1995 and it might be time to revisit.

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I feel your pain with no transfusion commitee, we don't either.

It never hurts to revisit the protocals but I would go into it armed with all of the numbers. # of surgeries with no blood use..those that used what was set up and those that needed more. Also education on the time frame to get blood if type ans screen is already complete. When I tell them 5-10 minutes if the screen was negative they are normally ok. One surgeon I was talking to about it laughed and said it would take them nearly that long to get to the blood bank.(must walk really slow).

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CT Ratios don't mean what they did many years ago. Back then, we crossmatched upon request ... mainly because in those days, we had to do a 'full' crossmatch every time creating a natural delay between order/need and crossmatch.

With the implementation of 'immediate spin only' crossmatches, the meaning of the CT Ratio changed.

Today, we (in 'my' hospitals) crossmatch only under the following conditions:

a) An order to actually transfuse (i.e. there is no such thing as 'hold')

B) Patients with atypical antibodies that would require a search that may take longer than, say, a half an hour OR for patients who are going to surgery (we have a 'we'll get you blood in 5 minutes' promise so we do what we must do to maintain that).

If a patient has atypical antibodies, sometimes, if certain criteria are met, we use the patient's plasma to screen the units. Since we have to allocate those units in our LIS, they are counted as a 'crossmatch'. This will skew our CT Ratio.

In addition, we crossmatch all Autologous Units (why wait?) ... another skew (but very minor).

So, the CT Ratio is not a universal standard, it is more of an internal indicator of activity. For us, increases are usually simply because we've had more than usual patients with atypical antibodies that we are able to use patient plasma to crossmatch with (i.e. not use expensive reagents).

Example: The CT Ratios for Cardiac OR and the Main OR run higher than the floors ... that's a given based on what I just told you about our protocols.

The CT Ratio is no longer a punative measure for the ordering physicians.

If you want to bring your CT Ratios down, then you need to look at your BB protocols and stop crossmatching when you don't need to.

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I agree with Joanne. Also, we do electronic crossmatch, so we wait until we have a transfusion order before setting up the blood. We only crossmatch ahead for antibody patients (because of the AHG crossmatch) or massive bleeds. So our C/T ratio has been 1.1 every month this year. Boring, so now I'll have to pick something else to monitor. :tongue:

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The only thing that worries me about that Joanne is, what if your patient has, for example, an anti-Jka that only reacts with Jk(a+b-) red cells, or an anti-Fya that only reacts with Fy(a+b-) red cells. Your cross-match compatible units may well be Jk(a+b+) or Fy(a+b+), and you wouldn't know, because they would be compatible. They could well boost the anti-Jka or anti-Fya (in my examples) and cause a delayed haemolytic transfusion reaction, particularly as the red cells in the units are in a preservative designed to maintain oxygen-carrying capacity at an optimum, but NOT in a preservative that is designed to maintain optimum antigen expression.

Edited by Malcolm Needs
As usual, spelling!
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What a coincidence that just this morning our Transfusion Committee had a discussion on how important was the end of the year C/T ratio average, then the issue appears on bbtalk! We average 1.29, but our transfusions are mostly oncology and in-house medical. Post-op transfusions tend to be from ortho and gyn procedures. I see the Tech Manual doesn't state an optimum value any longer. My thoughts are that 1.29 is pretty modest value and that if we had individual providers crossmatching but not transfusing, it would be reflected in our monthly C/T stats. I found an article on C/T values but it is somewhat dated (not that older research is any less valuable today-I definitely don't want to imply that, as others in this blog have done to their peril!) I was just wondering what the BB community-who read this blog-feels about total C/T and if it should continue to be a quality marker. The article reference was Clin Lab Haematol. 1983;5(4):379-85. thanks. John V

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Yes, well aware of the zygocity issue.

Ok, bear with me while I clarify our criteria:

n.b. We are using MTS, so testing is very sensitive and standardized.

During Antibody ID, we run heterozygous cell(s) to establish whether the patient's plasma will react at least 2+ (MTS).

We perform an extended crossmatch (MTS).

  • If the antibody fulfils the above criteria, the extended crossmatch is sufficient (no further testing).
  • If not, reagent antisera must be used to verify the absence of the antigen.

Our CT Ratio is 1.3 ... we have a lot of oncology/antibody producers.

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Well, I can see from where you are coming Joanne, BUT, although your antibody panel cells that have presumed heterozygous expression may react with the patient's plasma, don't forget that they are in a preservative designed for optimum antigen expression, but not optimum oxygen-carrying capacity, whereas I come back to my point that the red cells that you are cross-matching are in a preservative that is designed to preserve optimum oxygen-carrying capacity, but not optimum antigen expression. Your antibody panel cells that are, to use my examples again, Jk(a+b+) or Fy(a+b+) may well, therefore, detect an anti-Jka or an anti-Fya in your patient's plasma, but that does not mean that the patient's plasma will react in such a way that you will detect a Jk(a+b+) or Fy(a+b+) unit of blood in the cross-match, because the antigens may be degraded.

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Point taken.

But ...:rolleyes: ... if the antigen on the donor cells deteriorated to the point where a demonstrated strong, freshly produced antibody cannot detect it, why would an old chemically rich reagent be expected to be better? Some of these reagent antisera actually deteriorate over time as our QC records show ... which is why we have to do QC using reagent RBCs on each day-of-use.

Aside from storage issues, reagents from different manufacturers/cell lines/clones do not always correlate with each other.

The QC is the same:

Patient Plasma vs reagent RBC and vs donor.

Reagent Antisera vs reagent RBC and vs donor.

So, I put more value on a 2+ fresh antibody produced by the patient who is going to recieve this unit than a 1+ reaction from a stored reagent approaching it's outdate that is not really guaranteed to detect all antigen variations.

Edited by JPCroke
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Joanne, I like your initial response and agree with what you said. Unfortunately, we, in the blood bank don't see orders to transfuse. We only see crossmatch orders. It would be too time consuming for us to call on all crossmatch orders to see if there is also an order to transfuse. It would be nice if we could see the transfusion orders, as we too, use immediate spin and electronic crossmatch.

Although I understand that C/T ratio may not mean today, what it did years ago, but I feel like in my situation, the high ratio is indicative of antiquated ordering practices by providers.

Maybe one day we will have a transfusion committee where meaningful dialogue can take place to ensure best practice and proper resource allocation.

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I see.

We eliminated the 'crossmatch x units' orders ... they don't exist in our system. No purpose for them.

The only orders the MDs have to choose from are 'Transfuse RBCs', 'Transfuse Plasma', etc.

The MDs are oriented to this ... order only what you want to transfuse.

I must add that when we are performing pretransfusion testing for pre-ops, if the patient has atypical antibodies, we DO crossmatch 2 units and we call the surgeon to see if he/she thinks that more will be needed for the particular surgery so we can be ready with them ahead of time.

So, if you can change your order description to read 'Transfuse Red Blood Cells' and orient your staff, you can eliminate the double order system (crossmatch + transfuse) = less work for BB and the MD.

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I don't see the C/T ratio being punitive anymore either, but I do know that Cardiac pre-op orders will mess it up some. Our surgeons like us to have 4 units available for them and we do that because they will sometimes ask for 3 units up front. Even though we have I.S. crossmatching, it takes a little longer than they want to wait for us to "add-on" while they are waiting for the blood (paperwork!). We try to stay 2 units ahead if they start using and conversely, if they want us to have 6-8 units ready pre-op, we only crossmatch 4 units and wait to see how it goes.

Many cardiac surgeries now do not use anything at all - but you have to be ready for them - they can still get messy. But that kind of "crossmatch and wait" use pattern does increase your C/T ratio

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Thanks for the input. We do not have a transfustion committee (I know, GASP!) and our cardiothoracic surgeons are averaging a C/T ratio of 3.3! I have been watching this for 4 months now and before I call attention to it, I wondered if anyone else let's this slide. I know 20+ years ago, when I started in blood banking, we set up 8 units of blood for every open heart surgery, but now it's only 2 and most of those come back. Also, I believe or protocol heart surgeries was implemented in 1995 and it might be time to revisit.

We are starting a transfusion committee because it is required by CAP and JACHO and now by HFAP [our accreditation organization]. Before I was the pathologist and I were the 2 person transfusion committee. It does help to have one so the blood bank doesn't look like the bad guy when it comes to blood utilization.

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  • 1 month later...

Joanne, what do you do about surgery cases? We have a blood fridge in the OR and they routinely take units down there and bring back those not needed. Did you have to train them not to take blood unless they planned to transfuse it? How were you able to convince them that they would have blood available before the patient "bled to death"?

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Yes, well aware of the zygocity issue.

Ok, bear with me while I clarify our criteria:

n.b. We are using MTS, so testing is very sensitive and standardized.

During Antibody ID, we run heterozygous cell(s) to establish whether the patient's plasma will react at least 2+ (MTS).

We perform an extended crossmatch (MTS).

  • If the antibody fulfils the above criteria, the extended crossmatch is sufficient (no further testing).
  • If not, reagent antisera must be used to verify the absence of the antigen.

Our CT Ratio is 1.3 ... we have a lot of oncology/antibody producers.

Out of curiousity, who accredits your transfusion service?

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Malcolm, is there evidence that the difference between antigen stability in donor segments vs. reagent cells is actually significant or just no one has proven that donor cells are equally stable? I.e., is there evidence of this problem or just no evidence that it is not a problem? Is it consistent over all antigens or are some more affected--especially low-frequency antigens for which we rely on the crossmatch alone? Is it a linear difference over time, or logarithmic or...?

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No, there is evidence, albeit a bit sparce.

I remember Jill Storry, now working at Martin Olsson's laboratory in Lund, Sweden, and now famous throughout the world of Blood Transfusion, writing a paper about this, when she was just a humble Senior Biomedical Scientist at the NBS Bristol Centre. I'll try to cite the paper, but I'm really busy with various meetings and lectures (some of which I have yet to write!) over the next couple of weeks, so I can't guarantee a quick turnaround on this one.

It is certainly not consistent over all antigens. For example, the paper of which I am thinking, Jill's, was about Duffy antigens "going off" on storage, and, without doubt, the CR1-related antigens (Kn(a), McC(a), etc) are unstable upon storage. As for the low-frequency antigens, such as Di(a) in most populations, I am not at all certain that there has ever been anything published. A project for someone????????????

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Mabel, I've found Jill's paper. It is:

Storry JR. Long term preservation of red cell antibody identification panels in low ionic strength solution. Medical Laboratory Sciences 1987; 44 350-355.

In a reply to a letter I wrote to her about this paper, she cites another paper, which is:

Malyska H et al. Effects on blood group antigens from storage at low ionic strength in the presence of neomycin. Vox Sanguinis 1983; 44: 375.

I realise both of these papers refer to storage in LISS, but, at least it's a start!!!!!!!!!

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There was another study that looked at antigen stability of commercially-prepared panels, with the goal of validating the use of expired panel red cells in antibody identification tests. It was performed by a large group, and was published as an abstract in Transfusion. Particulars are

Hamilton, JR, et.al. Validation of Expired Red Cells for Use in Antibody Identification Tube Tests. Transfusion 2004; 44: S60-040C.

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We don't have a refrigerator in the OR.

Our promise is that blood will be ready in 5 minutes. We do what we need to do to fulfill that promise, e.g. crossmatch ahead if the patient has clinically significant antibodies.

(In those cases, we automatically set up 2 and call the surgeon ahead of time to see if more is necessary.)

Basically, they call for blood and then come get it ... they have no idea what we are doing in the BB.

Joanne, what do you do about surgery cases? We have a blood fridge in the OR and they routinely take units down there and bring back those not needed. Did you have to train them not to take blood unless they planned to transfuse it? How were you able to convince them that they would have blood available before the patient "bled to death"?
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