Probenstabilität

Probenstabilität is how long the material in the tube still gives a result that means anything. A sample is not inert. Cells go on metabolising, proteins degrade, some analytes fall apart in light and others shift as soon as the sample warms up or cools down too far. The analysis itself can be perfect and still return a value that describes the handling rather than the person, which is why this sits in the middle of Präanalytik.

There is no single answer because there is no single window. Every parameter has its own, and the spread between them is large. Some 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 so fragile that they are only reliable if the material is processed almost immediately or frozen. Whole blood and separated serum or plasma behave differently again, because as long as cells and serum stay in contact, substances continue moving between them. This is why a panel is only as stable as its least stable component.

Four things shorten the window in practice. Time is the obvious one. 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. Light matters for a small group of light sensitive parameters. Handling matters throughout, because rough transport or an unhappy draw produces Hämolyse, and a haemolytic sample can be rejected for some parameters no matter how quickly it arrives.

For a pharmacy this is really a planning question rather than a laboratory one. The gap between the appointment and the courier is the thing being managed, so 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.