The order of blood draw: its importance in blood sample collection
Healthcare practitioners working in blood sciences perform blood and other bodily fluids testing. Whether an order of draw is still required has been an ongoing debate within the profession. By reviewing evidence, researchers have now provided clear guidance for best practice that can be used to drive standardisation across Europe.
Over the last few decades laboratories have become more automated and reduced errors in the analytical process to very low levels (<10% of all errors). However, this means that around 90% of errors in the total testing process, defined as the process from conception of the need to test to interpretation of its results, now happen outside of the analytical process. The largest proportion of these occur in the pre-analytical phase – the phase from test conception to analysis. One step in this process is the action of blood collection.
When a patient requires blood tests, often more than one tube is required. These blood tubes may contain different additives which may affect certain results should they contaminate another tube. For this reason, an order of draw was established. However, the initial evidence that contamination was a problem was based on a study from 1982 using just five patients.
Recently there have been conflicting opinions as to whether following an order of draw is still legitimate in modern practice. In their opinion paper published in Clinical Chemistry and Laboratory Medicine, a group of researchers set out to review the evidence.
They found multiple studies to show that under ideal conditions for blood sampling, there was no effect from the order of blood tube collection on sample results – indicating that in this setting there was no requirement for an order of draw. Nevertheless, studies that looked at real world situations, where conditions are frequently not ideal, provided clear evidence that contamination does still occur.
Both facts led the authors to recommend that an order of draw remains part of the blood collection process, having resolved an on-going debate in the profession as to whether an order of draw was still required.
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