Hi All,  I would like to change our CSF differential to be preformed only when the WBC count is greater than 5.  Right now we do differentials on all samples no matter what the WBC count is.   I cannot find any documentation in the literature that this is ok.  I know of a few hospitals that do this.  If you do this what reference to you use to for documentation in your procedure.  Do you also report a comment as to why the differential was not done?

Thanks for your help.

We have a policy like that for whether or not to do CSF diffs, but I cannot find a reference anywhere around here. 

 

The protocol, like all P&Ps, was approved by our pathologist, so that should be good enough for any regulator.  If we had a question from a doc over a diff not being done on a normal WBC CSF count, I guess we would refer them to our pathologist.  But no one has ever complained as far as i know.

 

The basic reason for a diff being uneeded for a normal count, in my opinion, is that if the WBC is low, the diff is not going to add any useful clinical info.  (eg: For the same reason we do not do manual diffs on all of our CBCs that already have normal diffs from the analyzer.)

 

Scott

We only perform a differential if the WBC is greater than 5; we have a canned comment to attach to the report. We do, however, scan 2 stained cytospin slides to confirm the RBC count (CAP requirement) and to look for anything which might be clinically significant (malignant cells, bacteria, yeast).

Just wondering, how does scanning a cytospin slide confirm a RBC count?

Scott

Essentially, the cytospin is scanned for the ratio of RBC to WBC and compared to the chamber count to verify the accuracy of the chamber count.

Right - but if the chamber count was messed up - over or under diluted or the math done wrong or whatever, I am not sure how a cytospin ratio is going to check for that. Do you document QC for the hemocytometer counts?

Scott

The RBC confirmation is not QC. We perform manual QC for chamber counts (which does not, in fact, validate the accuracy of the chamber count-just because you fill the chamber correctly for the QC and count the chamber accurately does not ensure you will do the same for the patient).

 

An example of RBC confirmation:

 

The manual hemocytometer RBC = 50. The manual hemocytometer WBC = 25. For the RBC to be confirmed, the cytospin slide would show a ratio 2:1 for RBC:WBC.

 

If the RBC cannot be confirmed, the chamber count is repeated.

I was just curious if you used an external control material to "QC" the hemocytometer like we do. I have always thought that this was kind of a waste of time.

Scott