Coulter dilutions for high WBC's

[carol lou]

We are discussing dilutions for high WBC counts on the Coulter750. What value do you use as a cut off for the WBC dilution? What dilution do you use to get the WBC down to inorder for it not to interfere with the other parameters? WBC under 100,000? Under 50,000?Do you use the diluted values for the RBC, HGB, etc. Do you verify with spun HCT. Have you ever noticed a WBC to be higher on dilution than the undiluted value ? Thank you for your imput.

Carol Lou

[kjmt]

Hi Carol,

I found this article that may be interesting for you to read.

http://static.cjp.com/gems/labhem/7.4.Fernandez.PDF

We use a LH 780, and I'm not sure of the minor differences with the 750. It appears from the above article that WBC is linear up to 400,000....so I would think the max dilution you'd want to do is a 1:4. We rarely have to dilute for WBC, and if so, I can't imagine we'd ever need to do more than a 1:2.

I have questioned the same thing about the parameters being affected, hgb in particular. It seems like when the WBC gets around 100,000 that the RBC parameters will all have "R" codes. I came across this situation not too long ago while working alone on my shift. Since the patient was transfusion dependent, it seemed obvious to want to take the (more accurate) hgb value from the diluted run.... however I was told the following day that we can't do this because it's not in our procedure AND that since we rarely have this problem, that we will continue to only report the (false!) undiluted hgb. Ugh! So, I'm interested to find out what you learn about this!

Probably wasn't much help to you

[kjmt]

I should add that Coulter suggests to correct the RBC by subtracting the WBC result from the original RBC. Determine correct hgb, hct, mcv, mch, mchc by either using manual hgb-hct methods (calculate other parameters with corrected rbc) OR by method of plasma replacement (remove as much of buffy coat as possible) and all rbc parameters may be reported.

[colleenbennett]

We use an LH 780 so I'm not entirely sure about the 750 but our machine automatically corrects the RBC values if the WBC value is > 140. We have noticed that the hgb values given by the LH were consistent with those obtained from our blood gas analyzer whose method is not affected by high WBCs.

Before getting the 780 we would correct for the RBC parameters on any WBC value >100. We would then run the Hgb on our blood gas analyzer because the large number of WBCs would not interfere with the Hgb on that methodology. We performed a spun HCT and together with the corrected RBC and Hgb we could calculate all the other RBC parameters.

[eric1980]

Everytime I log into BBT or, now PLT, I learn something new.

My lab is using LH750, and at very high WBC, we do get a "R" flag on all our RBC parameters. We usually do a 1:1 dilution and will get a good result after that. As long as the WBC result is within the linear range.

But I am very interested in exactly how other labs correct the RBC parameters. What do you guys mean by subtracting the WBC value from the RBC value? Looks like I have to contact my local Beckman-Coulter representative soon.