WASHINGTON - The first inconclusive test for mad cow disease was most likely caused by human error and not by the test used in the government's newly deployed rapid screening test, said a senior executive with the test's manufacturer.
"What we are seeing right now is likely to be technician error," Brad Crutchfield, vice president of California-based Bio-Rad Laboratories, told Reuters in an interview late Thursday.
Using Bio-Rad's rapid tests, U.S. officials over the past week reported two inconclusive results that could not rule out bovine spongiform encephalopathy (BSE), or mad cow disease, in suspect animals.
The USDA this week cleared the two suspect animals of mad cow disease after retesting their brain samples using a more sophisticated and complicated immunohistochemistry test.
The USDA has approved five rapid-screening tests to detect BSE as part of an expanded program that aims to test 220,000 U.S. cattle by the end of 2005. Since the program began on June 1, the USDA has tested more than 8,500 cattle for BSE.
Crutchfield said Bio-Rad's tests are extremely sensitive and can produce false results if the brain samples are prepared improperly.
"Given the sensitivity of our test, we have a sample preparation test that has to be performed correctly," he said. "If for some reason that is not done correctly, there could be leftover protein that could lead to an inconclusive (result)."
Crutchfield anticipated fewer inconclusive test results as state and federal officials gain experience in conducting the test. Worldwide, an estimated 1 in 300,000 inconclusive Bio-Rad test results last year was a false positive, he said.
In Europe and Asia, scientists conduct the more sophisticated confirmatory test only after an animal has had at least two inconclusive rapid screening tests, he said.
But the USDA requires that a sample be sent to its lab in Ames, Iowa, for confirmatory testing after a first inconclusive test result.
"What you are looking for in a rapid test is correlation between multiple runs," he said, referring to the testing procedure in Europe and Asia. "If the second test is identical to the first test ... that sample would be sent off to confirmation testing."
U.S. cattle futures have seesawed this week as nervous traders awaited test results. The Chicago Mercantile Exchange contract for August delivery has fallen by about 4 cents to 85.075 cents per pound since last Friday.
Cattle industry officials have asked USDA to reconsider the government's practice of issuing daily results of inconclusive tests. But the USDA declined, saying earlier this week that it wants to be "very transparent with this issue" to avoid market rumors.REUTERS:
