The sample material to be sent for PCR depends decisively on the pathogen to be detected and the present symptoms or problem. Depending on the spread of the pathogen in the body and its excretion, different sample materials are suitable.
Pathogens that cause viraemia, parasitaemia or bacteraemia can be detected directly in an EDTA blood sample in this phase of the infection. Lithium heparin as an anticoagulant is less suitable because it can inhibit PCR. For blood samples as for other liquid samples, a quantity of at least 0.2 ml is required.
In contrast to bacteriological/mycological testing, sterile swabs without transport medium are recommended for PCR testing. If the pathogen concentration is low, swabs in medium can lead to false negative results. The swabs can be moistened with physiological saline solution for sample collection. So-called cytobrushes (brush swabs), which can be sent in an uncoated, sterile tube, are also suitable for PCR examinations.
For pathogen detection from faeces, sample quantities the size of a hazelnut are required. For some pathogens (e.g. coronavirus, Tritrichomonas foetus) we recommend collecting faecal samples over 3 days, as these pathogens are excreted intermittently with the faeces.
Other sample materials such as skin biopsies, organ material, urine, synovia, cerebrospinal fluid, bone marrow and lymph node punctates are best sent in sterile, uncoated sample containers for PCR investigations. Fixation solutions such as formalin or similar can lead to DNA degradation, PCR inhibition and thus to false negative results.