Does anyone have a literature reference for the exact procedure of platelet estimations. Currently our procedure reads to count 10 fields (100x) average and multiply by 20,000. We recently got a new scope with a larger Field of View. Since the size of field has changed, shouldn't our multiplication factor change? At a previous hospital I worked at some scopes we multiplied by 20,000 and some 14,000 due to the change in Field of View.

I am needing to update the procedure and wanted to make sure I had the correct value.

Of Course U should Change the multiplication factor according to the scope. Also some scopes are supplied with two types of eye pieces. One May give u a larger field and the other will be a smaller one.

Please Use as reference of Sysmex Platelet count. Also the factor may vary according to the RBC counts as well. ( i e MCV MCH MCHC )

We have found with our scopes (at 10 x 100, High power field) that a count of 14-40 corrisponds to a normal count. We know this is roughly adequate from comparison with accurate counts from our analyzer, which is something you should do regardless of the magnification used. What's important is how your manual estimate compares with actual counts.

If we cannot report out the analyzer count for some reason, we blank that result and report out an estimate as Low, Normal or High. You really cannot get a more precise estimate beyond that without using a hemacytometer. When you look at a field of plts and RBCs on a scope, you are arbitrarily comparing the number of platelets in the field to the number of RBCs. So the ratio of RBCs to platelets will also depend on the RBC count, NOT just the platelet count.

The key thing to do when scanning a slide, I think, is to check for for things like platelet clumps in addition to a rough estimate (lo-norm-high) for platelets and WBCs. That's all you need to decide if a follow-up is needed before releasing results. Don't worry so much about an "exact" estimate.

And this seems to be what you were looking for as a reference:

http://www.mlo-online.com/features/201105/tips-from-the-clinical-experts/review-of-platelet-estimates.aspx

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Edited April 11, 201312 yr by colleenbennett