Additional information

Additional information

In this section, medical professionals will find useful information on sample material, sampling and shipping of human samples.
Definitions
Serum
After the coagulation of fibrin and separation of the cellular blood components, the resulting liquid portion of the blood (plasma without fibrin)
Plasma
Liquid, cell-free part of the blood
Liquor
Liquor cerebrospinalis is formed as an ultrafiltrate in the choroid plexus of the cerebral ventricles and flows from there into the basal cisterns and then into the lumbar cisterna (descending) or along the cortex (ascending). The average volume for adults is 140ml with a daily production of around 500ml.
General requirements
The basis of any good analysis is the professional preanalytical phase. This includes that the patient is appropriately prepared, the material collection is carried out properly and the samples are then stabilized for storage and transport.
The sample material for the serological examination should always be taken sterile and sent to the laboratory immediately.
Patient preparation
The preparation of the patient influences the examination results. It is recommended that patients fast for 10 to 12 hours before a sample is collected. It is therefore advisable to take a blood sample in the morning between 7 and 9 a.m. Immediately before the blood sample is taken, the patient should not have undertaken any physical exertion (sit or lie quietly for at least 10 minutes) and the sample should be taken quickly and calmly.
Test material
Serum
If possible, blood serum should be sent in for antibody determinations. 0.5 ml of serum is required for testing.
The time until the onset of coagulation can vary from patient to patient (30-60 min.) To obtain serum, the blood should remain in a vessel without an anticoagulant at room temperature until it completely coagulates. The process can be accelerated by using coagulants (e.g. tubes with beads). The sample should then be centrifuged for approx. 10-15 minutes at approx. 1000 x g and the serum carefully pipetted off. The serum yield is about one third of the whole blood volume. Serum for the detection of antiviral antibodies is relatively stable when stored correctly. It can be kept for a short time (1-3 days) at 4-8 ° C and for longer term at -20 ° C. The sterility of the sample and the complete separation of the cellular blood components are important.

Whole blood
Whole blood without an anticoagulant should not be sent in as this inevitably leads to hemolysis. Severely hemolytic serum samples often show toxicity when used in test methods that work with indicator cells (see below).

Plasma
In exceptional cases, plasma is suitable for determining the antibody titer in the serum neutralization test if no serum sample is available. 0.5 ml of plasma is required for testing.
Plasma is obtained from anticoagulated whole blood. Heparin or EDTA are suitable as anticoagulants. The plasma can be obtained immediately after removal by centrifugation (approx. 10 min. At 1000 x g). It can be stored briefly (1-3 days) at 4 - 8 ° C and longer term at -20 ° C. The sterility of the sample and the complete separation of the cellular blood components are important.

Liquor
According to the place of origin and the direction of the CSF flow, "lumbar" CSF is not representative for all areas of the brain. The brain areas accessible by means of CSF diagnostics include in particular the hemispheres, basal ganglia, subpontine parts of the CNS, cerebellum and basal cortex.
When collecting the CSF, it must be ensured that there is no blood in the sample. Even small amounts of blood or blood components can falsify the results of the CSF test.
In principle, liquor in its native form must be transported to the laboratory as quickly as possible. For the serological examination, the CSF should be transported or stored at 4-8 ° C. CSF cells can be pelleted by centrifugation at 200g for 10min (4-8 ° C). The supernatant is removed in a sterile manner and transferred to a fresh tube.
Sampling
Blood collection
To avoid hemolysis, the vein may only be congested briefly before the puncture (max. 30 seconds). A closed blood collection system should be used to obtain sterile samples. A strong negative pressure in the syringe should be avoided in order not to burst the erythrocytes. Cannulas that are too fine should also not be used (in adults > No. 12). The cannulas used to draw blood must be disposed of immediately (risk of injury and infection). Blood should not be drawn from permanent venous or arterial access. When removing from the arm vein, do not knock or pump (clench or open and close the fist). To obtain plasma, use  tubes with anticoagulant, fill them to the mark and stir gently.

CSF puncture
The collection of cerebrospinal fluid must be carried out under strictly aseptic conditions. The doctor and assistant staff should wear a surgical mask to avoid droplet infection. The puncture site must be carefully disinfected. The CSF puncture is performed after local anesthesia at the lumbar puncture site, usually between the 4th and 5th lumbar vertebrae. After puncture with a CSF channel, the usual diagnostic amount (> 10ml) of CSF is removed.
Factors disturbing the analysis - toxicity (especially serum samples)
In test methods that work with indicator cells (e.g. FAVN test, etc.), the cells can die as a result of toxic influences on the sample material. Such tests may not be evaluable. The causes of toxicity can vary. Possible factors are severe hemolysis, lipemia, jaundice and medication. Therefore, it is recommended that patients fast for 10 to 12 hours prior to specimen collection. Unless necessary due to illness, the patient should not take any pharmacologically active substances before taking the sample.
Sample identification
An application form is required for each sample (see appendix), which must contain the following information:
  • sender (name, address)
  • patient (ID number)
  • sample material and amount
  • sampling date
  • anamnesis or reason for submission
  • desired examination (s)
The sample container must be labeled in such a way that it is possible to assign the individual sample to the corresponding patient via the application form (e.g. ID number or name). Samples that are not clearly labeled can only be processed by the diagnostic laboratory after the sender has confirmed the sample identity.
Sending of samples
The sample material should be sent to the laboratory as soon as possible. It should be refrigerated at 4-8 ° C until dispatch (serum 1-4 days) or frozen at -20 ° C for longer storage. Cooling during transport (regular mail or courier service within Germany) is generally not necessary.

Packaging according to dangerous goods regulations
This order regulates the transport of infectious substances (substances that are known or can be assumed to contain pathogens or are dangerous for humans and animals) as well as clinical waste and diagnostic samples.

Packing rules
(according to UN No. 3373 and packing instruction P 650)
  • sufficiently resistant that impacts / loads cannot cause damage / leakage of the contents during normal transport
  •  a sample vessel and an additional shipping vessel are required
  •  the shipping item (sample plus shipping container) must meet a drop test
  •  labeling of the envelope "patient sample".

Liquid substances
  • the sample container must be tight and may have a maximum filling quantity of 500 ml / mg
  • the shipping container (outer packaging) must also be tight and have an absorbent material which, in the case of liquid samples, is able to absorb the entire amount of sample
  • outer packaging: max. 4 l

Who is responsible in the event of a sample expired?
The sender is responsible for the goods to be transported (i.e. recourse obligation for the sender in the event of damage / costs due to improperly packed samples). For this reason, it is advisable to comply with the provisions of the dangerous goods ordinance, as the sample is safely packaged in this way.
Storage of samples at the Lab
Retention samples from the submitted material are kept by the laboratory for at least 4 months. Within this period, the sender can request additional examinations from the available material at any time if enough sample material is available for a further examination and the material is suitable for the desired test.