Explanation PCR results


The results of the PCR-test are presented with:

  • “+” : the virus is detected.
  • “-” : the virus is┬ánot┬ádetected.
  • “+/-” : the virus is detected but it is not clear wheather this is a (recent) infection or external contamination. This result counts as negative in the calculation of the percentage.
  • INV : during the execution of the test, it turned out that the material was┬ánot┬ásuitable for testing. This is usually due to aging of the material. These do not count in the percentage calculation. If there are too many INV in a sub sample, no percentage is calculated.

The mentioned percentage is based on the number of (succesfully) tested sub samples in combination with the numer of pieces per sub sample. Per sample 10×24 pieces of 10×12 pieces. If all sub samples are tested positive, a percentage and ‘>’ sign is mentioned. In these situations, the percentage may therefor be higher.

Do you also want to know a more exact percentage with higher percentages? This can be done by testing the same amount of pieces divided over more sub samples. Per example 20×12 or 20×6 pieces.

Cq-values are only given for PlAMV and TVX. The results of other viruses are mostly clear virus free or virus infected. That is why no Cq-values are given for these viruses.

Limits Cq-value PlAMV (to December 15th, 2020)
Cq 38-40; result “-”
Cq 33-37; result “+/-”
Cq 0-32; result “+”

Limits Cq-value PlAMV (from December 16th, 2020)
Cq 38-40; result “-”
Cq 34-37; result “+/-”
Cq 0-33; result “+”

Limits Cq-value TVX
Cq 35-40; result “-”
Cq 0-34; result “+”

Interpretation of the result of a contact or water sample
The results are presented with a Cq-value. The lower the value, the more virus particles have been detected in the sample. A value of 40 indicates that no virus has been detected in the sample. A negative result of a virus test on a contact or water sample is no garantee of the absence of virus.

A negative outcome of a virus test of the (sub) sample does not necessarily guarantee the absence of virus in the lot.