Order of Draw

Order of draw

Why must the order of draw be followed accordingly?

Order of draw is done to avoid cross-contamination and unreliable test results. 

How can this happen? Blood culture tubes are usually at the top of the order of draw to avoid contamination of the blood collected. This is because bacteria from non-sterile tube stoppers or shields may result in bacteria growth, which will show in the test result as a blood infection. This is why blood culture bottles must be collected first before any other tubes.

A tube with EDTA, for example, is rich in potassium and can cause an increase in potassium levels. Therefore, if a test for potassium is required, the tubes used must be those that are placed before those that contain EDTA. 

The same thing is true when a coagulation test need to be performed. Since tubes with clot activators can interfere with the results, tubes with light blue stopper must be used before other tubes.

Credit: ACoRD UM.