In one sentence
Serumgewinnung is the sequence that turns a drawn sample into serum, meaning complete clotting, centrifugation and separation from the cells. Where a pharmacy does not centrifuge, the laboratory carries it out and the pharmacy protects the sample until then.
Serumgewinnung is what happens to a sample between the draw and the analysis when serum is wanted. Serum is plasma without the clotting factors, which is why several routine parameters are specified for it.
The sequence for serum has four steps:
- The blood is collected into a tube that contains no Antikoagulans.
- The sample is then allowed to clot completely while standing upright.
- The tube is centrifuged once the clotting has finished.
- The clear serum is then held away from the cells, either by the gel in a Serum-Gel-Röhrchen or by being pipetted off into a secondary tube.
Each step exists for a reason and each one can be got wrong:
- Clotting has to finish before the spin, because a tube centrifuged too early continues to clot afterwards and produces fibrin threads that block the analyser and cost the sample.
- The spin has to follow within the window the laboratory states, because serum left in contact with the cells keeps exchanging material with them.
- Potassium rises and glucose falls during that interval, so a delayed number describes the transport rather than the person.
- Excessive force at any point produces Hämolyse, and a haemolytic serum is rejected for several analytes no matter how carefully everything else was done.
In most pharmacy settings the centrifugation and the separation are not done on the premises, and there is no reason they should be, because the laboratory has the equipment, the validation and the documented procedure for it. The pharmacy performs the draw, mixes as instructed, labels the tube and then holds the sample under the conditions the laboratory has specified until collection.
The processing is not the pharmacy's responsibility, but the window before it belongs entirely to the pharmacy. Time and temperature are set at the pharmacy counter rather than in the laboratory, and once a tube has stood too long or been carried in a hot car no later care can repair it.
So the collection times, the storage place and the courier rhythm are agreed as part of Probenlogistik before the service is offered, and the agreed window is written down rather than remembered.
This glossary entry is general information about German pharmacy law and practice. It is not legal advice. For binding guidance on your own pharmacy, contact your Landesapothekerkammer.
