The immunohistochemistry (IHC) test is a laboratory method that detects antibodies of
prions
Prions are misfolded proteins that have the ability to transmit their misfolded shape onto normal variants of the same protein. They characterize several fatal and transmissible neurodegenerative diseases in humans and many other animals. It i ...
(mis-shapen proteins thought to transmit
bovine spongiform encephalopathy
Bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, is an incurable and invariably fatal neurodegenerative disease of cattle. Symptoms include abnormal behavior, trouble walking, and weight loss. Later in the course of t ...
, BSE or mad cow disease) by exposing a brain sample to a stain that appears as a specific color under a microscope.
The IHC test is used by USDA researchers in their BSE surveillance program because they consider it the gold standard, providing a high level of confidence about the results. However, IHC tests are expensive and time-consuming. More rapid and less expensive testing alternatives (“rapid tests”) have been used in some other countries, but until recently
USDA
The United States Department of Agriculture (USDA) is the federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, and food. It aims to meet the needs of com ...
has viewed them as less reliable because they can deliver more false positive and/or false negative results than the IHC. However, in June 2004 USDA embarked on a greatly expanded BSE testing program to test more than 200,000 cattle over a 12-18 month period (compared with 20,000 in each of 2002 and 2003). It is now using rapid test kits at regional laboratories to conduct initial screening; any samples that test “positive” for BSE (which USDA terms “inconclusive”) must be subjected to an IHC test for confirmation.
References
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{{DEFAULTSORT:Immunohistochemistry Test
United States Department of Agriculture