Frequency of Antibody Investigations

[ribekak]

I had a question regarding antibody investigation frequency.

It's my understanding that many facilities perform investigations every 72 hours (every crossmatch) if the screen is positive. I was curious as to whether this is a universal policy, or whether there are exceptions (ie. only if they've been transfused since last AI).

I'm in the process of rewriting some of the protocols for our facility and I was hoping for some feedback in regards to this matter.

Thanks.

[pdavenport]

There are several different schools of thought on this. At my facility we obtain a new specimen every four days. The standards say the sample must be drawn within 3 days of the transfusion and that the day of draw is day 0. When we get a fresh sample from a patient with a previously identified antibody we run a mini panel of selected cells to determine whether any new alloantibodies have been formed. We don't bother to confirm the presence of the previously identified antibody because we're going to have to honor it anyway.

[ribekak]

Are there any guidelines or standards written to address this issue?

We currently don't investigate positive screens for patients (with a history of antibodies) unless the reactivity changes or the crossmatch is incompatible. Our pathologist is looking towards moving to a more conservative approach, which would entail a significant increase in workload.

I'm having a difficult time finding a definitive protocol.

[GilTphoto]

We currently don't investigate positive screens for patients (with a history of antibodies) unless the reactivity changes or the crossmatch is incompatible.

This is what we do. Our policy says it's not necessary, but several techs go ahead and perform a new panel anyway.

Gil

[galvania]

UK guidelines state that if the patient was transfused within 3-14 days, the sample is to be taken no more than 24 hrs before transfusion; patient transfused within 15-28 days, sample to be taken not more than 72 hours before transfusion; patient transfused within 29 days to 3 months, then 1 week before transfusion. In situations where patients are being repeatedly transfused, the antibody screen is repeated every 72 hours.

In France the guidelines state that a sample is valid for 72 hours period.

[John C. Staley]

If you are interested, the 24 ed of AABB Stds 5.13.3.3 states: "In patients with previously identified clinically significant antibodies, methods of testing shall be those that identify additional clinically significant antibodies."

I imagine CAP has something similar but I'll let someone else find that if they want.

There are a number of ways this is interpreted. My favorite is that you repeat the antibody screen everytime you get a new sample to see if the pattern of screening cells indicates a change and AHG crossmatch antigen negative units for the known antibody. If they are compatible you are good to go. If they are incompatible you do what is necessary to discover why. A number of facilities follow this policy, a number of others find it appalling that anyone would consider it.

[Eagle Eye]

We do similiar to what John does but our cutoff is 7 days. We repeat panel every 7 days unless we see change in pattern for our screening cells.

[ribekak]

Could I ask where the 7 days comes from? I've polled other facilities and it seems to range quite a bit. From 72 hours, 7 days, 14 days, 30 days to never.

[John C. Staley]

That variety of cut-off times seems to come from the comfort level of the individual supervisor and/or medical director, their back ground and experiences.

If I remember right the University of Michigan Transfusion Service did some studies on this quite awhile ago and that's where I first heard of the protocol I described above. I'm not sure where the data would be found but I would not be surprised if it is in a TRANSFUSION issue some where.

:coffeecup

[bbbirder]

I think that what you do will also depend on your staff. Do you have dedicated BBer's or generalists who rotate through?

Linda F

[ribekak]

We're a fairly large facility with a dedicated staff of blood bankers, no rotating through the core lab.

Just another question, I'm assuming that most facilities test every 7 days, etc., regardless of transfusion history. Is there any need to test if the patient hasn't been transfused since the last investigation? Or do hospitals simply test as a rule to avoid complication?