Platelets count is usually realised on EDTA anticoagulant. This one is sometimes able to generate platelets agregats. That is the reason why the first thing to do encountering thrombopenia is to check for agregats on blood thin smear. In case of positive result, a control can be asked using another anticoagulant. The most used is sodium citrate. A correction has to be applied to the automat result because blood is diluted in anticoagulant. But no one says those haematological automats are exact on citrate as they are on EDTA. That's what we wanted to check.