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BSE and scrapie: diagnostic flowchart

Where to send tissue samples or have samples taken, how samples will be tested, possible outcomes of testing and reported results.

Table showing reported result for testing outcomes from IHC and Western Blot testing.

IHC	Western Blot	Action?	Reported result
Positive	Positive		Positive
Positive	Inconclusive		Positive
Positive	Negative	Audit before reporting	Positive
Positive	Unsuitable		Positive
Inconclusive	Positive		Positive
Inconclusive	Inconclusive	Review material, consider options	Likely to be inconclusive OR unconfirmed
Inconclusive	Negative	Review material, consider options	Likely to be inconclusive OR unconfirmed
Inconclusive	Unsuitable	Review material, consider options	Likely to be inconclusive OR unconfirmed
Negative	Positive	Audit before reporting	Positive
Negative	Inconclusive	Review material, consider options	Likely to be inconclusive OR unconfirmed
Negative	Negative	Depends on submission route and whether there is an ELISA result	Negative OR unconfirmed
Negative	Unsuitable	Depends on submission route and whether there is an ELISA result	Negative OR unconfirmed
Unsuitable	Positive		Positive
Unsuitable	Inconclusive	Review material, consider options	Likely to be inconclusive OR unconfirmed
Unsuitable	Negative	Depends on submission route and whether there is an ELISA result	Negative OR unconfirmed
Unsuitable	Unsuitable	No action possible	Unsuitable

Surveillance

For passive surveillance, use the APHA Veterinary Investigation Centre, where samples will be taken and sent to APHA Weybridge for testing.

For active surveillance, send samples in the first place to the Screening Laboratory for rapid ELISA testing. The laboratory will discard samples that test negative or are unsuitable for testing. Samples that test positive, or produce an inconclusive result, will be sent to APHA Weybridge for confirmatory testing.

Testing

Fixed tissue only samples will be tested using Immunohistochemistry (IHC).

Fresh tissue only samples will be tested using Western Blot.

When both Fixed and fresh samples are available, they will be allocated to IHC or Western Blot testing, respectively.

Outcomes

Possible outcomes are:

• Positive

• Negative

• Sample unsuitable for testing

• Inconclusive result

If tested using Western Blot, a positive sample can be sent for genotyping.