The Clock Starts at Collection

Part of Clinical Laboratory (LAB) Training: Stability, Timing and the Clock.

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

Not when the sample reached you

Stability windows run from the moment of collection. Transport time is inside the window, not before it.

This is the single most misread requirement in trial laboratory work. A sample that arrives with forty minutes already gone does not get the full sixty.

Why the limit exists

Analytes change in whole blood. Glucose falls as cells keep consuming it. Potassium rises as it leaks from cells. Some peptides degrade within the hour.

The window is set so the measured value still reflects the participant, not the tube.

Read the collection time, then do the arithmetic

Before you start, work out how much of the window is left. Write that down.

If thirty minutes remain and the run in front of you takes forty, you already have a problem. Knowing it now lets you reorder the bench. Finding out afterward gives you a deviation.

Prioritize by window, not by arrival

The sample that arrived first is not always the most urgent. A sample with a two-hour window that arrived an hour ago is less urgent than one with a thirty-minute window that arrived ten minutes ago.

Sort by time remaining.

When the window will be missed

Do not race and hope. Decide.

Process it anyway and record the actual time, unless the manual says otherwise. A late sample with an accurate time stamp can be assessed by the sponsor. They may accept it, flag it, or exclude that time point.

What they cannot do is assess a sample whose true timing is unknown.

Never adjust a time to fit

Writing a collection or processing time that makes the window look met is falsification. It is not a small thing, and it is usually detectable, because times cross-reference against the site's source records and the courier's manifest.

A missed window is a deviation. A changed time is misconduct.

Ambient and frozen clocks differ

Some samples have a limit at room temperature and a longer one refrigerated. Putting a sample on ice may extend the window or may be forbidden.

The manual says which. Do not assume cold is always safer.