What influences platelet count within the normal range?

When I became a platelet donor about two years ago, the apheresis center was really excited because my platelet count was at the high end of normal, increasing the likelihood of getting two units of platelet concentrate out of one donation.

I recently had a CBC for my annual physical, and my platelet count was smack in the middle of the normal range.

In a normal, healthy person, what causes the platelet count to fluctuate? And is there anything I can do to increase it? Platelet donation is a big enough time commitment that I’d like to maximize the results, if possible.

As far as I know (and I both donate and collect platelets), there’s nothing you can do. An average platelet count is often good for a double or even a triple, depending on factors like height, weight, and hemoglobin/hematocrit. Two people who have the same numbers and whose machines are programmed the same may even have different yields when all is said and done.

Thank you for donating! Even single units are very much appreciated.

Is widely varying, or low counts on a regular basis (low enough that I can’t donate platelets) common? The low limit for donating platelets is 150,000. I’m often below that, as low as 100,000 or even 50,000. I’ve seen an oncologist who tested and said there is no concern, but he offered no explanation. I’ve been told I shouldn’t even bother retesting, they need whole blood and red blood cells too and they love me because I’m O+, but I wish I could donate platelets too.

Why are my counts so often low?

Thank you so much for responding, Silvorange! Tell me about programming the machine. What goes into that? I know they can change how hard it “pulls” because they almost always have to set it lower for me. What else?

I am kind of new to apheresis collection, having just moved over from whole blood collections in September. The machine we use in my region is the Amicus. We can collect single, double, or triple units of platelets, or a single or double combined with a unit of plasma.

When I program the machine, I put in the donor’s weight, height, and hemoglobin along with their average platelet count from the past few donations. Then I can start playing with the yield. If I am hoping for a triple, I will start by programming a yield of 10. If that setting makes the collection time go over 120 minutes, the volume of blood that is processed go too high, or the donor’s expected post-donation platelet count go too low, then I will try a little lower. If I have to go low enough that I know the triple isn’t going to happen, I will jump down to a double. With most people, I have a good idea of what to expect based on their past numbers.

Once the donation is started, sometimes I have to reset to account for things that slow the donation down. For instance, the machine might have predicted that double would take 99 minutes, but the donor has a small vein, or the needle is in at a wonky angle, the infusion rate needs to be slowed down. That could bump the time up over the 120 minute limit. In that case, I might change the settings to just go for a single.

Platelets do go up an down somewhat erratically. One of the reasons may be that they are a bit like a ‘stress hormone’ or ‘fight or flight reaction’. In other words, during a “stress” to the body, platelet numbers increase. That makes sense since many situations of “stress” (from an evolutionary perspective) may involve bleeding - it’s a good idea, then, to have plenty of blood-clotting platelets around at such times.

In terms of manipulating one’s platelet counts up, I doubt there’s anything that can be done on a moment’s (or day’s) notice. Mind you, acute blood loss bumps up the platelets, so you could give a red blood cell donation one day and a platelet donation on the next, by which time your platelet count may have risen in response to the blood loss from the day before.

Over the longer term, in addition to ‘stress’, platelets are also increased by the presence of (serious) inflammation in the body (e.g. rheumatoid arthritis, ulcerative colitis), iron deficiency, and having had the spleen removed (by surgery or even by “auto-splenectomy” as occurs in people with sickle cell anemia for example).

I know someone whose platelets dropped pretty low but have been slowly rebounding over the last few years.

Speculation:
1 - Diet (this person is a vegetarian)
2 - Virus (this person had some sort of mono-like virus a few years ago)

Do either of these things match your history?

Interesting. The first few times I tried to donate platelets, I failed the hemoglobin test. (That set me on a course that led to a hysterectomy, which took care of the anemia issue.) I wonder if that’s why my platelet count was so high when I first started donating.

Absolutely, if you had anemia, especially ‘iron-deficiency anemia’, the platelet count may well have been pushed up to impressively high levels.

It’s interesting that iron deficiency anemia, but less so other causes of anemia (except for acute blood loss), is particularly associated with high platelets (thrombocytosis); over one-quarter of patients in this study for example.