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Hi All,

I have a question, but firstly good old story time for some context. I came across a patient who had positive antibody screen on all three screening cells used (BioRad). I was concerned this may be an auto and pan-reactive, and required units. Performed a monospecific DAT, showing a positive reaction to IgG only. By this time antibody panel finished cooking and showed the patient may have anti-Fya , but couldn't do phenotype. By this time I was nearing my shift so handed it over to my colleague and asked for some units to be crossmatched. However, he refused as DAT was positive and said he rather send the sample to reference laboratory for them to crossmatch. The next day I crossmatched units to verify if it could have been done in our laboratory (just because I am sad that way), and turn out the unit I crossmatched was compatible (which I wasn't surprised about)

Question

Why does positive DAT (or the cause of positive DAT) sometimes interfere with IAT techniques (such as antibody panel and crossmatch) and sometimes it does not? If both use AHG, then wouldn't positive DAT with IgG cause antibody panels shows pan-reactive with red cells? But obviously it doesn't, but I'm trying to figure out why, and I'm sure the answer is quite obvious. 

My laboratory seems very hesitant whenever they see anything regarding autoantibodies or positive DAT, and thinks that sample cannot be crossmatched in-house and needs to be sent off without even trying to investigate. Hopefully, by me asking this question, I can explain it back to my colleagues (but obviously take all the credit).

Cheers in advance,

Jermin

 

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Have this patient been transfused ? If it had, then maybe the allogentibodies coated with transfused cells, then caused the pos DAT, which would show mixed field .

 Or the autoantidies are weak, they can only coated with red cells, no free autoantibodies showed on the circulation, then they will not interfere with the crossmatch and screen.

Edited by yan xia
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8 hours ago, yan xia said:

Have this patient been transfused ? If it had, then maybe the allogentibodies coated with transfused cells, then caused the pos DAT, which would show mixed field .

 Or the autoantidies are weak, they can only coated with red cells, no free autoantibodies showed on the circulation, then they will not interfere with the crossmatch and screen.

I prefer the second scenario.  I have seen this quite often.

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16 hours ago, Jermin said:

Hi All,

I have a question, but firstly good old story time for some context. I came across a patient who had positive antibody screen on all three screening cells used (BioRad). I was concerned this may be an auto and pan-reactive, and required units. Performed a monospecific DAT, showing a positive reaction to IgG only. By this time antibody panel finished cooking and showed the patient may have anti-Fya , but couldn't do phenotype. By this time I was nearing my shift so handed it over to my colleague and asked for some units to be crossmatched. However, he refused as DAT was positive and said he rather send the sample to reference laboratory for them to crossmatch. The next day I crossmatched units to verify if it could have been done in our laboratory (just because I am sad that way), and turn out the unit I crossmatched was compatible (which I wasn't surprised about)

Question

Why does positive DAT (or the cause of positive DAT) sometimes interfere with IAT techniques (such as antibody panel and crossmatch) and sometimes it does not? If both use AHG, then wouldn't positive DAT with IgG cause antibody panels shows pan-reactive with red cells? But obviously it doesn't, but I'm trying to figure out why, and I'm sure the answer is quite obvious. 

My laboratory seems very hesitant whenever they see anything regarding autoantibodies or positive DAT, and thinks that sample cannot be crossmatched in-house and needs to be sent off without even trying to investigate. Hopefully, by me asking this question, I can explain it back to my colleagues (but obviously take all the credit).

Cheers in advance,

Jermin

 

Does your laboratory staff have the necessary procedures to follow for this scenario?   I think flow charts work very well for things like this.  

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16 hours ago, yan xia said:

Or the autoantidies are weak, they can only coated with red cells, no free autoantibodies showed on the circulation, then they will not interfere with the crossmatch and screen.

 

8 hours ago, Malcolm Needs said:

I prefer the second scenario.  I have seen this quite often.

Thanks for your replies and I believe I understand. So for this particular patient, we did send the sample to the reference laboratory which found the patient had autoantibodies, as well as alloantibodies (anti-Fya ). 

 

3 hours ago, R1R2 said:

Does your laboratory staff have the necessary procedures to follow for this scenario?   I think flow charts work very well for things like this. 

No. I will see if I can talk to my senior, but before that, I would like my colleagues to be able to understand why positive DAT or having autoantibodies may not be the end of the world, and that they could try and crossmatch the units in-house.

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