Thursday, August 10, 2006

It ain't what you do.....

... it's the way that you - or in this case vets doing Tb testing - do it.

So concludes Debbie Reynolds, the Chief Veterinary Officer in a news release today, which targetted veterinary practitioner's 'application' methods of the intradermal tuberculin skin tests as a factor in the drop in cases, rather than the Lelystad tuberculin used in their guns. Well that will make friends and influence people won't it?

A quote from the report:
"Debby Reynolds, the Chief Veterinary Officer, who was asked by Ben Bradshaw in June to undertake a review of the apparent fall in the number of new TB incidents, has concluded that there has been a real reduction in the number of new TB incidents, but that it is too early to determine whether this is a temporary phenomenon or likely to become a sustained trend. Dr Reynolds has considered whether the switch in tuberculin supply from that manufactured by the Veterinary Laboratories Agency to that purchased from Holland could have caused this reduction. She has concluded that the small difference in performance between the two tuberculins is not significant enough on its own to have had such a significant impact, particularly against the background of the evidence in the DNV Consulting report about the variation in the way the test is carried out. Further analysis will be carried out to try to reduce the level of uncertainty around these conclusions."

Whaaaat? Would that be the ' small difference' which provoked Defra's Feb 2006 re-interpretation chart? The loss of about 2mm of sensitivety / specificity which made a Pass on the old interpretation chart into either an Inconclusive or a Reactor - from February? No mention then of the batch (s) which provoked not a single reaction at all, or was that down to 'testing procedure' as well? And did all those veterinary practioners who now face retraining, have a mental block together, all of them forgetting how to test cattle just after Christmas en masse . Must have been a good party.

And how delicious that the Lelystad tuberculin has been in the country from June 2005, and in use in the RBCT areas during the Krebs' trial, but without the benefit of Defra's new update and 'markedly tighter' (veterinary opinion, not ours) interpretation chart. What will that do to the already tortured data of the Krebs results - all of which rest on the number of cattle breakdowns, as tested and recorded by SVS and LVI personnel, who are now to undergo 'retraining' - and using serum which the CVO herself says 'has a small difference in performance"?

Madame, with the greatest of respect, a 2mm difference in performance is not 'small'. With only 5mm to play with, or under severe interpretation 3mm, as the late Tony Hancock pointed out, "It might only be a small amount to you, but it is the difference between life and death for someone". Or in this case some cattle, and certainly the difference between pass or fail, and a herd breakdown and a clear test.

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