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Strong Cold Agglutinins and CBC results


mjohnred

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Currently our procedure for Cold Agglutinins is to put CBC tube in 37 degree heat block for 15 minutes and if that doesn't work to extend time for 15 more minutes.  However there are times when this will not work if the titer is high on the Cold Agglutinin.  I'm trying to find out what other facilities do in this situation.  We have tried doing warm saline replacement, but currently our procedure for a saline replacement states that RBC count before replacement should match the RBC count after the replacement within 5%.  This rule will not work with a Cold Agglutinin, so if you do a warm saline replacement how do you confirm you are putting out accurate results.  Also what results do you report from the replacement?  I'm trying to standardize our practice so everyone is on the same page.  Your input is greatly appreciated and if you can share a procedure that would be great too.  Thanks for your help 

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3 hours ago, kimannez said:

You may want to try a prewarmed 1:5 dilution and use the hemoglobin to determine if the dilution is acceptable.  It always worked for us!

Hi Kimmannez, I was curious to know what your acceptable range is between the neat hgb result and the diluted hgb result. Given that 

the strong cold agglutinin would significantly alter the rbc distribution of the neat specimen as compared to the diluted specimen my guess is that 

your range is broad. How was this range established and do you know of any references? Thanks for any info.

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On ‎1‎/‎31‎/‎2018 at 9:42 AM, kimannez said:

The cold agglutinin didn't interfere with the HGB result because it used a harsh lyse and light absorbance.  I think our limit was +/- 0.4 g/dL, but I don't know the reference (I've been out of the lab for a couple of years).

Thank you for the info kimannez. I was not sure if the strong cold agglutinin would alter the distribution of rbc's prior to the lysing step significantly enough as compared to the diluted aliquot specimen. But I can see where a "harsh lyse" would be more useful. Can I ask, what instrument was in use for this testing?

Edited by rravkin@aol.com
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We were using the Sysmex analyzers as the time.  They use a sodium laurel sulfate detergent in the hemoglobin channel which fully lyses the red cells and also breaks up lipids.  I see your concern with uneven RBC distribution--I have heard of cases where the RBCs are so agglutinated that it doesn't even aspirate a uniform sample.  I would guess in that case you might wash an aliquot of the sample before diluting? 

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A few comments:

  • Beware of running strong Cold agg samples initially cold and the subsequently warm.  Most Haematology analysers sample from the bottom of tube, with strong Cold Aggs (especially those anaemic) this may result in a significant volume of concentrated RBC's being removed from tube, when sample warmed and re-analysed then patient may become significantly more anaemic! (So we only allow 5 g/L difference between runs).  We use Middleware rules to identify these known patients and prevent these samples to be run 'cold'.
  • Why worry about not reporting RBC, MCV, MCH etc in this small set of patients, clinically they need accurate WBC / Diff, Hb & Plts.
  • Beware of using warmed diluents, this will cause MCV shift (Dependant on analyser), so will need to validate procedure.
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