Why does the blood sample need to be collected within 15 minutes?

Why does the blood sample need to be collected within 15 minutes?

In order to preserve the quality of the whole blood sample and ensure an appropriate additive to blood ratio, the entire contents of the tube need to be collected within 15 minutes of the initial tube puncture. 

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In cases where your patient may need a break in order to achieve the 14-17mL required total sample volume, it is ok to perform two separate venipunctures at different times as long as both tubes are collected the same calendar day and each cell-free DNA tube is collected within a 15 minute timeframe.