Probenstabilität

Probenstabilität is how long the material in the tube still gives a result that means anything. A sample is not inert, because cells go on metabolising, proteins degrade, some analytes break down in light and others change as soon as the sample warms up or cools down too far. The analysis itself can be perfect while the value describes the handling rather than the person, which is why Probenstabilität belongs to Präanalytik.

There is no single window and therefore no single answer, because every parameter has its own and the spread between them is large. Some analytes are comfortable for a day or more in the refrigerator, some need the sample separated within a short time of collection, and a few are only reliable if the material is processed almost immediately or frozen. Whole blood and separated serum or plasma behave differently again, because substances continue moving between cells and serum for as long as the two stay in contact. A panel is therefore only as stable as its least stable component.

Four things shorten the window in practice.

1. Time is the obvious one, because every window is counted from the moment of collection.
2. Temperature is the one that goes wrong most often, in both directions, since a tube left near a window or a radiator and a tube that has been allowed to freeze are both damaged.
3. Light matters for a small group of light sensitive parameters.
4. Handling matters throughout, because rough transport or a difficult draw produces Hämolyse, and a haemolytic sample can be rejected for some parameters however quickly it arrives.

For a pharmacy this is a planning question rather than a laboratory one, because the thing being managed is the gap between the appointment and the courier. Appointment times are set against the collection time and not the other way round, and the whole Probenlogistik is built backwards from the last handover of the day.

What must never happen is that the pharmacy estimates the window itself. The akkreditiertes Labor publishes stability, storage temperature and required handling for each parameter it offers, and that specification is the only source that counts. Where the schedule cannot meet it, the honest answer is to move the appointment rather than to send the sample and hope.