"The USDA National Veterinary Services Laboratories (NVSL) in Ames, Iowa, has determined that the inconclusive screening test sample reported on Nov. 18 has tested negative for BSE upon confirmatory testing.

"The Nov. 18 sample is the first that has tested inconclusive under an APHIS protocol announced in August that calls for public reporting of screening results only after two reactive screens. NVSL used the immunohistochemistry (IHC) test, an internationally-recognized gold standard test for BSE, and received a negative result on Nov. 22. Because the Nov. 18 screening test results were reactive in both the first and second screens, NVSL scientists made the recommendation to run the IHC test a second time. On Nov. 23 they reported the second IHC test was negative. Negative results from both IHC tests make us confident that the animal in question is indeed negative for BSE.

"APHIS began an enhanced surveillance program on June 1 and to date has tested over 121,000 samples for BSE. Screening tests are designed to be extremely sensitive and false positives are not unexpected. APHIS has reported three inconclusives including the Nov. 18 sample and all have tested negative on confirmatory testing."