What is the most accurate lab method to measure platelet count (tube type, etc). last results varied by 30% in 1 hour; prescription is based on lab result.?

Automated cell count: Automated cell counts are generally accurate, however, in some cases, due to medication or disease process, platelets form clumps that can affect the accuracy of the count. When clumps are detected, a sample may be collected in a different anti-coagulant to prevent clumping and obtain a more accurate count.

Draw in citrate: The best method is to count the platelets manually. Look at the platelets under high power, count 10-15 fields, take the average and multiply by 18. Sometimes when blood is drawn in edta, the platelets can clump. Drawing the blood in citrate prevents clumping. Hope this helps.