decrease in plt count and increase in pH of apheresis plts

[Jives]

we are currently having a problem with our apheresis platelets....upon issue when we collect our pH and plt count we have noticed a DRASTIC decrease of the platelet count and an increase in pH (i have never seen a pH increase with storage!!!).....the products are drawn on a COBE TRIMA and the platelet counts are run on 2 different sysmex xe 2100, pH is run on abl 800 flex.....nothing seems to be amiss about the machines? my question is could this happen if there was a problem with the ACD used or a problem with the lot of kit used????

here is the most perplexing example:

drawn 8/8/11

plt count 8/9/11 approx 1500 on all 3 bags of a triple pH = 7.11

plt count 8/10/11 approx 1000 on all 3 bags and pH = 7.63

any ideas what could be happening??:confused:

thanks, jane

[Norbert Ahrens]

Are the samples drawn with comparable techniques? Differences could result in incorrect platelet counts.

The pH is said to be influenced by the agitation frequency. I have heard of blood banks that solved a similar phenomenon by reducing the frequency.

Best regards,

Norbert

[Jives]

most of the samples are drawn in a similar fashion, by stripping the tubing and heatsealing off a segment to test. however, if the unit is outdated the techs usually just cut open the segment attached to the bag and "pour" out what they need. thanks for the response!

[heathervaught]

Jane, your analyzers can't tell the difference between "live" and "dead" platelets - in its eyes, any particle that meets the criteria of looking like a platelet is a platelet. What we have noticed is that we get lower counts when platelets are stressed and have started to stick together (not visible to the naked eye, of course), then as they relax and become happy with their environment, they will become un-stuck, and the platelet count will be higher. We usually see the inverse of what you describe though...the platelet count is lower on samples taken shortly after collection, then higher after 24 hours of agitation, when the platelets have had time to adjust to life in a storage bag.

Here's where I would start: have you checked out the implicated donors for your "weird" products? You may find that you have a couple of frequent donors who are causing the observed phenomenon. Does your Sysmex report MPV? Is it higher in the samples with lower platelet counts? This would be positive evidence of the "sticky" platelet theory.

[Deb]

We also have two different models of Sysmex instruments. What I found was that one consistently reported values significantly lower than the other. To minimize impact of one more variablilty in the process we have all of our pre-donation samples and product QC samples tested on the same model.... You may want to check the correlation of the two hematology instruments using platelet samples. A 7% disparity between instruments has a much bigger impact when you are testing levels at x10<11> vs. X10<3>. You might be surprised!