Why Chain of Custody Is a Clinical Task

Part of Research Nurse (RN) Training: Specimens and Chain of Custody.

About 2 minutes. Free, in your language, no account needed.

Why this matters

A sample is a participant's contribution. It was taken from their body, once, at a moment that will not come again.

If it is mislabeled, mishandled or lost, that contribution is gone. You cannot go back and take the Week 4 sample in Week 6.

What chain of custody means

An unbroken record of where the sample was, and who had it, from collection to analysis.

Collected from this participant, at this time, by this person. Processed this way, at this time. Stored here, at this temperature. Shipped on this date, received on that one.

Every handover is a point where the chain can break, and every handover is recorded for exactly that reason.

Labeling

Label at the bedside, with the participant present. Not at the desk afterwards from memory and a list.

Check the identifiers on the label against the participant, the same way you would check a drug. Sample mix-ups almost always happen between the bedside and the bench.

Never label a tube before you know whose blood is going into it.

Timing is part of the sample

For many assays, the time of collection is as much a part of the data as the volume. A PK sample without an accurate time is often useless.

Record the actual time, not the scheduled one. If the sample was due at 14:00 and taken at 14:11, the record says 14:11.

That eleven minutes may be within tolerance or outside it. Either way, it is the truth, and only the truth can be interpreted.

In practice

You draw a timed sample two minutes late because the line was slow.

You record the actual time. You do not round to the scheduled time to make the record look tidy, and you do not omit the delay.

A sample that is known to be two minutes late is usable. A sample recorded at the wrong time is quietly wrong forever.

What this looks like when it goes wrong

A busy clinic pre-labels tubes for three participants to save time. Two participants arrive together.

One sample is drawn into the wrong tube. Nobody notices, because everything else is correct.

Two participants now have laboratory results that belong to each other. There is no way to detect it and no way to correct it.

Key takeaways