George attempted to answer this question about thrombocytopenia, which appeared on the ASCLS Consumer Forum, in November of 2008
I am a medical technologist. My platelet count has been running around 102,000/uL for the past few years. This year Quest Diagnostics did my blood work and the count was 87,000. I thought it may have something to do with the EDTA, so I had it rerun with both EDTA and citrated plasma and the counts were 95,000 and 98,000. I even diluted the EDTA specimen with saline 1/1 and reran, with the result the same. Everything looked normal on the blood film. We estimated the platelets in ten fields and came up with an average of 9 platelets/field. The formula we use is to multiply the average by 20,000, and the resulting estimate from that was 180,000. My WBC, RBC, HGB, HCT, MCV, MCH, RDW, etc. are all normal. I have no obvious symptoms of bleeding or bruising. Any clues as to my low count?
George’s answer in November, 2008
If, as you report, you have no symptoms of bleeding, it is likely your low platelet count is simply normal for you and requires no further workup.
If you do have bleeding, you may choose to have a platelet function workup; platelet aggregometry. You could have an inherited platelet disorder such as Bernard-Soulier syndrome, whose symptoms range from mild to severe. If you have some form of pseudothrombocytopenia such as platelet clumping or platelet satellitosis, which occur in about 0.1% of people, it would almost certainly show up in your peripheral blood film. It is of course possible that your platelets are only clumping in the instrument, however this would generate an elevated MPV, which you do not mention. As for that blood film platelet estimate, it could simply be inaccurate in the sense the wrong formula is being applied. I suggest you recheck in using a different microscope and check the multiplication formula, which varies by microscope.
His response, same day
Thank you so much for your response. To answer your questions, I do not seem to have any unusual bleeding or bruising. My MPV ranges from 8.1-8.7. Also, here is an alternate platelet estimate formula: Count platelets in 10 fields, multiply the average by HGB, and then multiply by 1000. With this formula 9 x 16.4 (HGB) x 1000 = 147,600. I ran EDTA plasma, citrated plasma, and a 50/50 (EDTA and saline) x 2. All results correlated.
George’s follow-up, next day
Thank you for the follow-up. Except for your thrombocytopenia, all your CBC results are within typical reference intervals. I’d like to direct you to a web site maintained by Dr. James N George, University of Oklahoma with databases that relate to thrombocytopenia;http://www.ouhsc.edu/platelets/index.html. This may provide you with some helpful information, and you may sign up and ask questions.
The most likely explanation for your chronic thrombocytopenia is that this platelet count is normal for you and requires no current follow-up.
According to Dr. George, a number of us have low platelet counts for no discernable reason. He reassures physicians that people experience life-threatening bleeds only when their count is below 10,000/uL.
Next most likely is that you are taking a drug that induces mild thrombocytopenia. Several drugs may have this effect through direct or immune mechanisms. Quinine-based drugs are often implicated. Consider any long-term drugs you may be taking.
Third most likely is low-grade chronic immune thrombocytopenic purpura in which your platelets are being consumed by a platelet-specific autoantibody. This condition is uncommon but not rare, and it waxes and wanes. This can be confirmed through (expensive) direct and indirect platelet antibody testing, which is available on referral from the immune thrombocytopenia laboratory at the University of Alabama at Birmingham.
A fourth possibility is that your thrombocytopenia is inherited. It could be interesting to follow up with platelet counts on your first-degree kindred. This seems to be rare, but there are some reports linking lifelong moderate asymptomatic thrombocytopenia to a chromosome 10 polymorphism. [Blood 2000;96:118.]
Relative to visual platelet estimates, many labs assign microscope-specific multiplication factors. They generate automated platelet counts from several normal healthy individuals, perform 1000X platelet estimates on blood films from these individuals, and divide the instrument platelet count by the number of platelets averaged from ten acceptable monolayer areas. The dividend is the multiplication factor. They then average the results from the various blood films. The factor varies among microscopes as a function of field diameter and magnification, and usually hits somewhere between 10,000 and 20,000.
Because you have no symptoms and your platelet count is not a threat to you, you may prudently choose to make no follow-up. In this case, the best course is to “wait and see.” Monitor yourself for easy bruising or other forms of mucocutaneous (systemic) bleeding, and check your platelet count once a year.
A December, 2009 follow-up
I just wanted to give you an update on my low platelet count that we communicated about a year ago. I went into my annual employer wellness screen with the following results 79,700/uL and 82,200/uL. The rest of the CBC was normal, however no MPV was reported.
I have not had bruising or bleeding, I am very active walking, running, carpentry work, swimming and fishing. I just turned 55 years old and feel very healthy. I was somewhat disappointed because I actually expected my platelet counts to be normal this time. I discontinued many of the supplements I suspected may be contributing such as fish oil and ginkgo biloba. I take no pharma products. I do drink a fair amount of coffee and use tobacco products occasionally. I still suspect that the anticoagulant and time element may be a factor. Quest still does my blood work. We collect and ship a plastic EDTA tube. I would appreciate any comments you may have based on this year’s results.
And finally, George’s December, 2009 response
Thank you for your update. I am sorry you didn’t see a rise in your platelet count over this past year. I want to reassure you again that this is very likely a count that is simply “normal” for you, however I would, for your peace of mind, recommend you see a hematologist to learn whether you may in fact have a low-grade form of ITP or a slowly developing bone marrow production condition (though the rest of your CBC is healthy and negates that idea). I suggest this as it appears you’ve eliminated the possibility of a drug response. If you don’t mind revealing to me your location, I will be happy to make a referral if I happen to know someone.
Since thrombocytopenia is a common problem, do you mind if I summarize your message (stripped of personal identifiers) on Fritsma Factor, www.fritsmafactor.com? I may receive a helpful response from one of the hematologists who monitor the site.
I received a final follow-up giving permission to post our exchange and contact information enabling me to recommend a physician.
My husband had a similar low platelet count with normal resu
My husband had a similar low platelet count with normal results from a work up. I discovered looking online, that ginkgo biloba can cause low platelets and he was taking that suppliment. He discontinued the ginkgo biloba, his platelets came back up and have been fine since.
An average of 9 platelets per field seems low to me. Of cou
An average of 9 platelets per field seems low to me. Of course, it depends on the microscope’s optics. We used a simple procedure to arrive at our “conversion factor” which is 12 using a 100x objective. So, with an average of 9 platelets/field – 9 x 12 = 108,000. Matches pretty well with the original count.