Ask the FDA 2010 Synopsis on AABB Web Site

[AMcCord]

Crossmatch incompatible because: ABO incompatible donor chosen

Type discrepancy in your AB patients: AB subgroup with anti-A1 or how about an antibody such as anti-M, -N, P1

[JOANBALONE]

For the incompatible major crossmatch

1. ABO discrepancy

2. Antibody showing dosage such as Jkb.

3. ??

[Liz]

Excellent 5 replies:

1. Aakupaku the donor has a positive DAT
   
2. Aakupaku the patient has Ab againt low frequency ag presnt on the donor's cells
   
3. Malcolm the patient is A sub and has anti-A1, the donor is A1
   
4. AMcCord the patient and donor are ABO incompatible
   
5. JoanBalone the patient's antibody is showing dosage, the donor is homozygous while the sc cells are hetero for the given antigen.
   

Thank you very good!!!

[Avid123]

Here is a copy of the question and the answer given by Penelope Meyers - Division of Laboratory Services, Survey & Certification Group, Center for Medicaid & State Operations at CMS:

"Question 4: We perform all routine testing using gel technology. We also perform electronic crossmatches.

For patients in whom clinically significant antibodies have been identified, is it sufficient to perform only a gel antiglobulin crossmatch? Does this satisfy the CLIA requirement to perform a test to detect ABO incompatibility?

MS. MEYERS: For this question, before I start, I would like to just make the comment that the answers that I will be giving to the questions today are based on the CLIA regulations. However, I would like to remind the audience that many laboratories choose to obtain their CLIA certification through a CMS-approved accreditation organization, of which there are six. One of which is AABB. These laboratories must follow all the requirements of their chosen accreditation organization which may be more stringent than the CLIA requirements.

Now back to the question. Actually, these CLIA requirements for crossmatching are based on the FDA requirements for crossmatching, and FDA and CMS have collaborated in preparing the answer to this question. The simple answer is that

the IgG gel card does not fulfill the requirement to demonstrate ABO incompatibility. There are two issues involved here.

First, the labeling clearly indicates that the IgG gel card is for direct and indirect antiglobulin tests. In other words, detection

of cell-bound IgG antibodies. While the limitation section of the package insert states that some IgM antibodies may react,

this limitation should not be interpreted to mean that the card is capable of detecting all IgM antibodies, particularly ABO antibodies. Secondly, the IgG gel card is a low ionic test system and there have been reports that ABO incompatibilities,

due to IgM antibodies, can be missed when the antibodies are weak and the test is low ionic strength. While we

acknowledge that there is continuing debate on this topic, but with the knowledge of these reports and in the absence of

data from the reagent manufacturer to support the use of a low ionic strength system for detection of ABO incompatibility

due to IgM antibodies, we believe it is not appropriate for users to omit some kind of test to detect these incompatibilities.

And for eligible patients, an electronic crossmatch would fulfill the requirements. An immediate spin crossmatch, of course,

is an acceptable method for all patients.

MODERATOR: Thank you, Penny. Can I ask, because I could not hear everything that you just said, but did you respond to

the part about sufficient to perform only the gel antiglobulin crossmatch, that first part?

MS. MEYERS: No, it is not sufficient to perform only the gel antiglobulin crossmatch because that does not fulfill the requirement to detect ABO incompatibilities."

There you have it. Straight from the horses mouth. The specific CFR is "21 CFR 606.151©- Procedures to demonstrate incompatibility between the donor's cell type and the recitpent's serum or plasma type."

I wonder if we are in compliance? We have HCLL for our TSIS (Transfusion Service Information System). The compatibility truth tables are set up so that we can set up an allow, forbid, or allow with an over ride for product selection. Our system is set up so that an incompatible RBC donor type could never be allowed to be even chosen for a patient, much less crossmatched and issued. Does the cover the compliance issue? Or should we be doing IS crossmatches as well as gel crossmatches for patients with antibodies?

[Mabel Adams]

I am old enough to want to clarify the distinction between a major crossmatch and an antigloblulin crossmatch. Back in the day (probably of whole blood transfusions 1970's and before), both major and minor crossmatches were performed. A minor crossmatch is the donor's serum/plasma against the recipient's cells. A major crossmatch is what we all do now: recipient's serum/plasma against the donor's cells (barring electronic, of course). An antiglobulin crossmatch could theoretically be either major or minor depending on the reactants used as described above. We can't change the terminology unless everyone on BBtalk agrees!

Pardon if this is not apropos to other countries' (non-US) usage of the terms.