Tuesday, June 05, 2007

Mea Culpa

I recently wrote about the Bush administration's determination to keep a meatpacker from testing all its animals for BSE or the mad cow disease. My take on the story was based on an AP article which stated:

The Agriculture Department regulates the test and argued that widespread testing could lead to a false positive that would harm the meat industry.

This turns out to be incorrect. Hilzoy from the blog Obsidian Wings sent me the actual brief of the case and also a link to Stuart Buck's blog post on the same topic.

These show that the Department of Agriculture based its arguments not on the possibility of false positives (the test showing that the animal is diseased when it is not) but on false negatives (the test showing that the animal is healthy when it is not). Most tests have the likelihood of producing false negatives and/or positives. The BSE test kit the meatpacking firm wished to use was argued to produce a very large likelihood of false negatives for the following reasons (from the government's consolidated memorandum, via Obsidian Wings):

"As discussed previously, the vast majority of cattle that are processed into beef in the United States are less than 24 months old. See Ferguson Decl. ¶ 5. However, the average incubation period for the BSE disease is five years, meaning that on average it takes five years from the date a cow is infected with BSE for the cow to show any outward clinical signs of the disease, such as abnormal posture, inability to walk, or other impaired coordination. See id. Given that the earliest point at which current BSE testing methods can detect a positive case of BSE is only two to three months before a cow would demonstrate clinical signs of the disease, see id. ¶ 10; Rippke Decl. ¶ 9, testing all young normal-looking cattle for slaughter, as proposed by plaintiff, is not practical and offers no animal health or food safety value because testing a young infected animal with the current methodology would likely produce false negative results, Ferguson Decl. ¶ 10.23.

In short, if this argument is correct the use of the BSE kit in the manner the meatpacker wanted would not have provided useful information about the safety of its beef. Thus, the case is more akin to trying to prevent fraudulent advertising than to trying to stop a firm from offering additional services its competitors are not interested in offering.
Cross-posted at the TAPPED.