WASHINGTON -- The U.S. Department of Agriculture's decision to hold off on declaring inconclusive or "false positive" test results for bovine spongiform encephalopathy until two rapid screening tests raise red flags may come as a relief to beef industry leaders concerned the announcements could create panic over mad cow disease. Previously, the agency had announced inconclusive results after only one screening.
Implemented earlier this month, the change does not alter any aspect of the enhanced surveillance program other than the timing of announcements, and was not made in response to criticism from either industry groups or USDA's Office of Inspector General, emphasized Jim Rogers, a spokesman for USDA's Animal Plant Health Inspection Service (APHIS).
"The rapid tests are three well tests, meaning they were always designed to be run three times," he said. "Previously, we were announcing inconclusive results after a single test. Now, if we have a reactive [result] on the first test, we'll run a second and a third. If either of those react also, we'll announce an inconclusive result and send the animal to be analyzed with an IHC [immunohistochemistry] test."
USDA's enhanced BSE surveillance program, which plans to test 268,000 head of cattle by mid-2005, has endured criticism on several fronts since its June 1 launch. USDA's Office of Inspector General questioned whether the agency's sampling program was effectively covering animals considered to be at highest risk for BSE, while some in the livestock and supermarket industries complained that regular announcements of inconclusive results would unnecessarily alarm consumers, driving them away from beef products.
"We made the decision to announce inconclusive test results, rather than wait for confirmatory testing, because we simply feel we owe it to the industry, the markets and the general public to be as transparent as possible during this process," John Clifford, deputy administrator for USDA's APHIS told SN last month, before the policy change went into effect. "We don't feel that this policy needlessly alarms the public because we have taken the most important step to protect public health, which is the removal of specified risk materials from the food supply."
The rapid tests were designed to be both quick and highly sensitive. These qualities have allowed USDA to be more ambitious in its goals for screening large numbers of cattle, but notably resulted in two "false positive" scares within a month of implementation, both on carcasses that later, using APHIS' more time-consuming "gold standard" IHC test, were determined to be free of BSE.
Rogers added that the new announcement protocol will make U.S. procedures more similar to testing programs in Japan and Europe. There, the beef industries have been contending with the threat of BSE for almost a decade.
"The whole reason we were announcing inconclusive results after one [rapid] test was because we were just starting. So we essentially took the most cautious route," said Rogers. "Now, with 30,000 tests under our belt and 60 days' worth of data, it's just natural that we would now go with how the test is designed."
APHIS has said it will continue to announce inconclusive results on its Web site if two out of three rapid screening tests are reactive because it remains concerned about rumors and leaks that could potentially surround the more thorough IHC tests, which take five to seven days to complete.
By using the enhanced rapid testing program to sample 268,000 cattle by mid-2005, officials at APHIS said they will statistically be able to detect one positive case of BSE for every 10 million adult cattle, with a 99% confidence level.
"APHIS is constantly evaluating the enhanced surveillance program," said Clifford. "We understand that as the program moves along, it may need to be tweaked to ensure optimal results."
