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From: TSS (
Date: November 4, 2004 at 1:05 pm PST

November 4, 2004


Scientists in FDA's Center for Veterinary Medicine have evaluated two
commercial test kits that are designed to detect animal proteins in
animal feed. A January 26, 2004, HHS Press Release entitled Expanded
"Mad Cow" Safeguards Announced to Strengthen Existing Firewalls Against
BSE Transmission
, announced
that FDA would continue to support the development and evaluation of
feed tests for detection of materials prohibited for use in ruminant feeds.

The discovery of a Canadian-born cow with Bovine Spongiform
Encephalopathy (BSE) in the State of Washington in December 2003 raised
awareness of the need for increased screening of animal feed to ensure
the absence of prohibited animal proteins in ruminant feed. Scientific
evidence has demonstrated a clear link between the practice of feeding
ruminants, such as cattle, the rendered remains of other ruminants with
the spread and dissemination of BSE.

Since the Food and Drug Administration does not have pre-market approval
over veterinary diagnostic devices such as feed test kits for detection
of prohibited animal protein, the Office of Research in FDA's Center for
Veterinary Medicine (CVM) initiated a study to evaluate the performance
characteristics of several commercially available test kits. The study
included two tests that used lateral flow, or dip-stick diagnostic
devices designed for general use, and two that were designed for use by
laboratory personnel. This CVM UPDATE presents the results of the FDA's
completed evaluation of the two lateral flow test kits; Neogen
Corporation's Reveal for Ruminant in Feed test and Strategic
Diagnostics Inc.'s (SDI) Feedchek test.

CVM researchers found that Neogen's test was 100% selective when
conducted by multiple analysts. Therefore, this test never gave a false
positive result. The test was able to detect animal protein down to only
1%, which was the level stated in the label guarantee.

CVM researchers evaluated Strategic Diagnostics Inc.'s test and observed
variable selectivity that seemed to be related to difficulty in reading
the test. The test exhibited 62% selectivity when conducted by one
analyst and 97% selectivity when conducted by another analyst.
Therefore, the test reported false positives in 3% and up to 38% of the
samples. The test was able to detect animal protein to the level of 0.1%.

FDA also identified critical issues with reading the results for both
test kits. The color development begins when the test strips are placed
in solutions extracted from the feed sample. Neogen's test strips were
accurate only when they were read 15 minutes after color development had
begun. SDI's test strips were accurate between 3 and 5 minutes after
color development had begun. Reading the SDI test longer than 5 minutes
after color development has been initiated can potentially result in
false positive reactions, as test strips turn positive after 5 minutes.
Therefore, when using these test kits, it is important to take the
readings at the appropriate time intervals.

These critical pieces of information were not contained in the package
inserts of the test kits FDA evaluated, and could potentially lead to
incorrect interpretation of the test strips, resulting in a false
negative determination if read too soon (both Neogen and SDI), or a
false positive determination with the SDI strips if read after 5
minutes. The Neogen Corporation has already incorporated this change
(reading the strip 15 minutes after initiation of color development)
into their package insert.

These test kits can be an important tool for surveillance and quality
assurance although they appear to be less sensitive than feed microscopy
and polymerase chain reaction (PCR) techniques that are capable of
detecting at least 0.1% bovine meat and bone meal.

Definition of terms:


False positive samples are true negative samples that were
incorrectly identified as being positive.


False negative samples are truly positive samples that were
incorrectly identified as negative.


Selectivity is the capacity to detect true negative samples.


Sensitivity is the capacity to detect true positive samples.


Issued by:
FDA, Center for Veterinary Medicine,
Office of Management and Communications, HFV-12
7519 Standish Place, Rockville, MD 20855
Telephone: (301) 827-3800 FAX: (301) 827-4065
Internet Web Site:


this reminds me of irradiating meat products in place of simply making
a safe product. are we replacing or attempting to replace rapid TSE
testing cattle with this commercial test kits that are designed to detect
animal proteins in animal feed? hope not...


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