My question: when would you rule out B*4441 by allele frequency?

1) Both alleles are CWD alleles (Cano et al. 2007), and this is our current standard for HR results.
2) The NMDP allele frequency tables show that 4402 is very common in the US (high frequency and rank), 4441 is not listed.  However, being new to HR typing, we are nervous about using this data over the CWD standards.
3) Allele frequencies.net shows that B*4441 has the allele frequency of 0.000 for the US.
4) Literature searches and HistoCheck show that B*4441 differs from B*4402 by 2 nucleotides and 2 amino acids.

Thank you for any advice or discussion!

Since our lab is now offering high-resolution DNA typing to support our university’s program, it would be great to connect with similar labs. Possible topics: reporting NMDP codes and CWD alleles, high-resolution typing techniques such as HD-SSO technology, and how/when to report allele groups, etc.

I’d appreciate forum responses or personal e-mails. 
Thanks~
Carley

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shelman

Posted: Fri Jun 06, 2008 1:36 pm
Thank you to all those ASHI members who completed the CPT typing codes survey. Here is a link to the survey results.

http://www.surveymonkey.com/sr.aspx?sm=t6WBkRMVtxCbZgKuDw2zrOfI67OCcqYt06dum7QZfVs_3d

All of your comments were read and discussed by the CPT codes task force. Responses are given below. Many comments were similar, so rather than responding to each comment, the responses were combined into a single response for each issue.

Responses to survey comments from the ASHI CPT Task Force:
Several questions or comments from the survey were about creation of new CPT codes for other testing. The proposal presented only addresses the HLA typing codes, but the task force is working on other proposals for antibody and crossmatching. We would like to submit proposals to the AMA for these tests as well. If you have comments, data, or references that you think will be useful, please provide it through the forum or to members of the task force.

There were also questions and comments regarding creation of CPT codes for MICA and KIR. Changing CPT codes is a labor intensive and political process. Codes for MICA and KIR will be considered after HLA typing, antibody testing and crossmatch changes have been submitted. Those proposals will most likely be considered sometime next year. Specific information in the literature (references) supporting clinical utillity and documented data on numbers of these tests performed would be appreciated by the Task force and would facilitate the process.

There were a number or comments related to the molecular codes that are used for HLA testing. The Task Force working under the premise that ALL histocompatibility specific codes should be in the histocompatibility/tissue typing section - currently 86805 – 86849. These codes would replace/eliminate the need to use any codes in the molecular section. If the coding proposal submitted is accepted by the AMA, they would be the official AMA codes specifically for HLA typing by any method. It would not be necessary to use any molecular codes because the HLA codes would include all HLA typing codes.

A couple of people thought that we should have a code for a complete typing at Class I and Class II rather than or along with locus specific codes. We thought that the current method is much more flexible, but not terribly complicated. There are more and more instances of typing for single loci or for different combinations of loci (ABDR vs ABC and DRDQ). This would allow the flexibility to bill appropriately for the loci tested.

Several comments were related to the definition of antigen resolution typing. We are defining antigen resolution typing as low resolution molecular typing or serology. The purpose of the assay is to define the antigen, in most cases for listing on UNOS. While the technology is different, the answer is essentially the same.

Intermediate resolution typing was another area of concern for a few people. This term is less well defined than high resolution or low resolution. There is no proficiency testing for intermediate resolution for this reason. It was the consensus of the task force that this should not be a separate code. It most cases, it should be coded for using antigen level resolution.

There were a number or questions and comments regarding the use of the term “high resolution typing” rather than “allele resolution typing”. We struggled with the terminology here, but ultimately decided that this term better describes the typing performed to rule out all but one common well defined allele per chromosome at each locus. All rare alleles would not need to be ruled out before the testing could be coded as high resolution.

The task force also struggled with whether DRB3/4/5 should be separate from DRB1 at antigen level and whether antigen level resolution for DQA and DPB and/or DPA were appropriate. We will continue to look at these issues.

In answer to the questions about whether to use the codes once or twice per locus, the intent of the proposal is that the codes would be used once per locus (i.e. high res typing for A2 and A33 would have one charge for the A locus)

The greatest number of comments were related to the coding for testing for a specific HLA antigen or allele by itself (disease association, drug sensitivity, or vaccine study). This proposal did NOT have a separate code for testing for a single antigen or allele, but proposed the use of the appropriate code for the locus in question. In the proposal, a request for testing for B27 antigen would use the same code that would be used to test for the B locus at antigen level resolution as part of a complete HLA type. Overall, most of those who responded to the survey (79%) agreed with this approach. However, most of the comments preferred using a separate code for single antigen or single allele testing. We will continue to consider this option.

-Peter

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dannyy

Posted: Thu Feb 14, 2008 3:27 pm Post subject: B-cell Antiglobulin Crossmatch Reply with quote
Many years ago our lab played around with using AHG in the B-Cell cytotoxicity crossmatch, with mixed results. Some cells seemed to be overly susceptible to the reagent and had high cell-death backgrounds in all sera, while others did just fine. We’re planning to evaluate B-cell-AHG again, and would apprecaite hearing others’ experience and advice.

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awhiteley

Posted: Mon Dec 01, 2008 1:46 pm
I think the main issue with B-Cell crossmatching is the CD32 receptors and the non-specific binding of IgG by the FcgR. Does your lab already do a B-cell Flow Crossmatch?

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dannyy

Posted: Wed Jan 21, 2009 1:47 pm
Yes, we perform a B-cell Flow XM, but there are some applications where our customers prefer a cytotoxicity crossmatch.