Does anyone use the simple math equation for correcting hemoglobin due to interference from lipemia, high wbc or icterus?  I saw the webinar from Sysmex "Letting go of the Rules of Three" and that was the first I had heard of it.  Currently we are doing a plasma blank or plasma replacement method.  I have tested the math in parallel with the other two methods and it is good.  My problem is I cant find a reference to cite other than the webinar.  There is a source on the screen shot "Pathology, 1991 (23)".  I searched the Journal of Pathology for 1991 and still cannot find it.  Does anyone have a procedure for this?  If so do you not report the MCHC and MCH when you do the correction?

corrected hemoglobin=(mcv x rbc)/(2.98x10) 

Thanks in advance for any input.

 

 

I would be interested in this also as I have never heard of a calculation to correct a Hgb in this way.  Is it based on Trig levels?

Certainly by using:  corrected hemoglobin=(mcv x rbc)/(2.98x10)  you are only basing the Hgb on what it would be for a NORMAL relationship to the MCV and RBC.  It seem like this would only be a valid Hgb estimate for persons with normal RBC, MCV and Hgb.  (Simular to how blood gas machines calculate the Hct from a Hgb.)

The normal way to correct for lipid interference is to do a saline replacement.  That's not too complicated and I believe it gives fairly accurate results, including the other indices.

Scott

Forever ago we used a calculation.  You would spin the sample down, then run the lipemic plasma for hgb measurement.

Then calculate:  True hgb = original hgb - ((plasma hgb x (1 - hct as a decimal))

I have no idea where this calculation came from, but it did always the plasma replacement method.  In my opinion, doing any kind of calculation is just silly when you can just replace the problematic plasma with diluent/saline. Using plasma replacement, you don't have to recalculate any of the indices, either.

Nicole

 

Hi Scott,

The webinar https://www.sysmex.com/crc/Webinars/Pages/LearnMore.aspx?WebinarID=75&Upcoming=0 says it is based on a constant ratio (2.98) between the MCV and MCH.  You are correct this formula can only be used if the MCV is normal. 

Laurel

Laurel,

The presenter for the webinar you cited wrote our hemoglobin correction procedure. There are successive steps in the procedure where a plasma blank and a plasma replacement are done if the prior step do not return an MCHC < 37.0. I'm not sure why she designed it that way but I suspect that anytime you manipulate the specimen there is a possibility that error can be introduced into the end result. Which may be why she favors the calculation because no sample dilution or other error can occur there.

Dan

It would be easy to see if you had poor technique resulting in a dilutional error doing the plasma replacement based on consistent or inconsistent WBC, RBC, and platelet counts.  If you're really bad at it, those won't match the original specimen.

Hi Dan,

You are correct, I think she favors this because of what you said.  Also, she stated in the webinar how (as we all know) difficult it can be when you have interference from an extremely high WBC count to remove that plasma accurately.  So yeah, not just lipemia.  It can also be used for Icterus and High WBC interference too.

Is there any possible way you would share that Hemoglobin correction procedure with me?  If not, maybe you could cite the references.  I already have a plasma/saline replacement and hemoglobin blank procedure.

Thank you,

Laurel

We use the plasma blank method.  It's not too difficult.  I found that a lot of the new techs we were getting were math challenged.  I created an Excel worksheet where you simply plug in the data and the corrected HGB and the RBC indices are calculated for you.  Yes, I verify the Excel calculations vs. manual calculations on a regular basis as required.  The spreadsheet is password protected so the formulas can't be altered.  You can print it too, if you want.