Editing Platelet (section)

===Measurement===
Platelet concentration in the blood (i.e. platelet count), can be measured manually using a [[hemocytometer]], or by placing blood in an automated platelet analyzer using particle counting, such as a [[Coulter counter]] or optical methods.<ref name="Stiff">{{cite book |last=Stiff |first=Patrick J. |url=http://www.ncbi.nlm.nih.gov/books/NBK262/ |title=Clinical Methods: The History, Physical, and Laboratory Examinations |date=1990 |publisher=Butterworths |isbn=978-0-409-90077-4 |editor-last=Walker |editor-first=H. Kenneth |edition=3rd |location=Boston |pmid=21250105 |editor-last2=Hall |editor-first2=W. Dallas |editor-last3=Hurst |editor-first3=J. Willis}}</ref> Most common [[complete blood count|blood testing methods]] include platelet count in their measurements, usually reported as [[complete blood count#Reference ranges|PLT]].<ref name="NHLBI">{{cite web |publisher=National Heart, Lung, and Blood Institute (NHLBI) |title=Platelet Disorders: Thrombocytopenia |date=24 March 2022 |url=https://www.nhlbi.nih.gov/health/thrombocytopenia |access-date=2022-11-18}}</ref>

Platelet concentrations vary between individuals and over time, with the population average between 250,000 and 260,000 cells per mm<sup>3</sup> (equivalent to per microliter), but the typical laboratory accepted normal range is between 150,000 and 400,000 cells per mm<sup>3</sup> or 150–400 × 10<sup>9</sup> per liter.<ref name="NHLBI"/><ref name="Stiff"/>

[[File:First and second wave of platelet aggregation.png|thumb|On for example optical densitometry, a first and second wave of platelet aggregation is seen, in this case for an [[adenosine diphosphate|ADP]]-initiated aggregation. ]]

On a stained [[blood smear]], platelets appear as dark purple spots, about 20% of the diameter of red blood cells. The smear reveals size, shape, qualitative number, and [[clumping (biology)|clumping]]. A healthy adult typically has 10 to 20 times more red blood cells than platelets.