##################### Bovine Spongiform Encephalopathy #####################
I posted this to cjd voice message board and got an interesting comment
from someone in the medical field and I thought I might share it with
A response has been posted to your article on "CJD Voice Discussion Group".
The URL for the response is
lab tech's comment
Mon Nov 29, 2004 07:07
Thanks for posting this interesting article. I'm a retired (just
recently) medical technologist that worked in the hospital laboratory
setting for 30 years in hematology, chemistry, microbiology, serology,
and blood bank departments. A former co-worker of mine died from CJD two
years ago. Bob was in his early sixties. Needless to say, CJD has
touched my life in a personal way.
I'd like to comment on portions of the article above:
ARTICLE QUOTE: "Asked whether state officials were notified, USDA
spokesman Ed Loyd told UPI the agency had not released any information
about the cow in question. Loyd also said the false positives on the
rapid test were not unexpected. Since June, the USDA has reported three
false positives out of more than 121,000 cows tested."
MY COMMENT: As a lab scientist, I have seen false positives AND false
negative results from tests that I have run myself. However, of those
times, there was an interfering substance responsible for the false
positive results and there was a reaction was too weak to measure that
yielded a false negative result. I have looked at the methodology of the
BioRad test, along with its acceptable standard deviation range. I
obtained the category cut off points and their standard deviation ranges
from a recent newspaper article. The news reporter failed to obtain (or
mention) some numbers of the entire numerical range. For a lab tech that
is always concerned with acceptable control values and acceptable
standard deviation ranges, this is a glaring omission. All numerical
possibilities MUST be included in the range. Here is the BioRad range as
it should be:
0.00 - < 0.03 ??? (Not listed in the article)
0.03 - 0.15 is NEGATIVE
> 0.15 - 0.18 ??? (Also not listed- what class do these numbers fall into?)
> 0.18 - < 0.80 is INCONCLUSIVE
0.80 and above is HIGHLY SUSPICIOUS
As you can see from these category ranges, hundreths of a point could
mean the difference in a negative or an inconclusive result.
Inconclusive results would necessitate more testing, while negative
results would receive no further testing. I would like to know exactly
WHAT substance could interfere with the test and cause an inclusive
result, as happened with the last cow. Brad Crutchfield, vice president
of Bio-Rad Laboratories the company that manufactures the mad cow
rapid-screening test, told Reuters: "After two inconclusive results, you
have a much higher rate of confirming (mad cow disease)" in the final
test. He said the accuracy of Bio-Rad's test was over 95 percent.
ARTICLE QUOTE: Moser said despite USDA's reliance on the IHC test
results, repeated negatives on that test does not necessarily rule out
the cow being infected.
"The reason for this is that the IHC test ... is done on a different
piece of tissue" than that used for the rapid test, he said. Prions, the
pathogen thought to cause mad cow disease, tend to concentrate in a
region of the brain called the obex, so the different outcomes of the
different tests could be due to sampling a brain region that contains
little or no prions. This could be made worse if the animal had lay dead
for several days before its brain was collected. The brain might be so
degraded that it would be difficult to locate the obex region for
confirmatory testing and a sample might mistakenly be taken from a
region that contains no prions.
"So with these samples, the confirmatory testing would be even less
reliable, not because of the confirmatory test itself, but because of
the sampling," he said.
MY COMMENT: Excellent points!!! The confirmation results are worthless
if the sample was not obtained from the proper area of the brain where
infected prions are known to congregate. This is just common sense, and
you sure don't have to be a rocket scientist to figure this out. Also, I
can't help but wonder how many microscope fields they scanned before
pronouncing a negative result. I'm of the opinion that the USDA doesn't
want to find another positive BSE. Therefore, they won't. .................
Re: lab tech's comment
Mon Nov 29, 2004 07:47
thanks for your comments. i am very sorry to hear about your
friend that died from CJD.
>A former co-worker of mine died from CJD two years ago. Bob was in his
early sixties. Needless to say, CJD has touched my life in a personal way.<
what did Bob do in the medical field? anything that could have
possibly exposed him to the TSE agent?
There is a false sense of security in the medical field that
this agent has only spread to a handful of victims by this
route. BUT i dispute this assumption due to the fact
of the lack of CJD surveillance and follow-up there after
of each victim, plus lack of autopsies.
Terry S. Singeltary Sr. wrote:
> ##################### Bovine Spongiform Encephalopathy
> Experts doubt USDA's mad cow results
> By Steve Mitchell
> Medical Correspondent
> Published 11/24/2004 4:34 PM
> WASHINGTON, Nov. 24 (UPI) -- U.S. Department of Agriculture officials
> said a cow that initially tested positive for mad cow disease was
> found to be negative on follow-up tests, but both domestic and
> international experts told United Press International the way the
> agency handled the situation leaves them skeptical about the validity
> of the results.
> "The testing process does indeed make experts scratch their heads,"
> said Markus Moser, a molecular biologist and chief executive officer
> of the Swiss firm Prionics, which manufactures tests for detecting mad
> cow disease, also known as bovine spongiform encephalopathy.
> "I think some, but not all, BSE people internationally have some
> degree of cynical de facto doubt about everything the United States
> does or doesn't do, mostly as a result of seeing so many similar
> situations where countries at risk deny and deny and deny and then end
> up having big problems," said Elizabeth Mumford, a veterinarian and
> BSE expert at Safe Food Solutions in Bern, Switzerland, a company that
> provides advice on reducing mad cow risk to industry and governments.
> Several countries, including Germany and Austria, that had been
> thought to be free of the disease, found out it was circulating in
> their herds after they initiated large-scale testing.
> The U.S. cow in question tested positive last week on two so-called
> rapid tests manufactured by Bio-Rad Laboratories in Hercules, Calif.
> The USDA said Tuesday the animal had tested negative on more
> sophisticated confirmatory tests called immunohistochemistry or IHC
> John Clifford of the USDA said in a statement that the negative IHC
> results "makes us confident that the animal in question is indeed
> A U.S. veterinarian knowledgeable about mad cow tests told UPI that
> experts she has spoken with are "very, very skeptical about" the
> USDA's negative test result.
> The veterinarian, who requested anonymity because she feared
> repercussions for speaking out against the USDA, said the skepticism
> arose because the agency did not run another kind of mad cow test
> called a Western blot. The test sometimes can pick up positive cases
> that IHC misses and the agency has used it in the past to rule out
> suspect cases.
> Moser said a Western blot test would make sense for the United States,
> where the prevalence of mad cow is thought to be low. Other countries
> -- including Australia, New Zealand, Canada and Mexico -- that are
> either free of the disease or have low rates, have elected to use the
> Western blot as part of their surveillance programs, he said.
> The veterinarian said concerns also have emerged because the USDA has
> not made a sample from the cow in question available for examination
> by outside experts. She added that the USDA did not notify state
> officials, as officials previously said they would about positive
> results on rapid tests.
> Knowledgeable people are saying "wait a minute, this doesn't add up
> here," the veterinarian said.
> At stake is the $70 billion U.S. beef industry, including a $3.3
> billion export market. More than 60 countries, including Japan, closed
> their borders to U.S. beef last December after the first -- and so far
> only -- U.S. case of mad cow was detected.
> Asked whether state officials were notified, USDA spokesman Ed Loyd
> told UPI the agency had not released any information about the cow in
> question. Loyd also said the false positives on the rapid test were
> not unexpected. Since June, the USDA has reported three false
> positives out of more than 121,000 cows tested.
> Bio-Rad spokeswoman Sam Kennedy told UPI the company was unfamiliar
> with the details of this incident and thus could not comment.
> Mumford said experts were surprised the USDA did not send samples from
> the cow in question for independent analysis by one of the three
> worldwide labs recognized as the foremost authorities on mad cow
> testing by the World Animal Health Organization. One of these
> facilities is located in Weybridge, England, where the USDA had sent
> the first U.S. case of mad cow disease for confirmation in December 2003.
> Loyd said USDA officials who would know whether USDA planned to
> release a sample for verification by an outside party could not be
> reached Wednesday.
> "Full transparency and cooperation would certainly promote the idea
> internationally that the U.S. is doing everything it can do," Mumford
> said. "But somehow the U.S. consumer doesn't seem to think that way,
> or has been appeasable at least up until now, so there seems to be no
> impetus to do anything more."
> The concern is humans can contract a fatal brain illness known as
> variant Creutzfeldt Jakob disease from eating beef products
> contaminated with the mad cow pathogen.
> Moser said despite USDA's reliance on the IHC test results, repeated
> negatives on that test does not necessarily rule out the cow being
> "The reason for this is that the IHC test ... is done on a different
> piece of tissue" than that used for the rapid test, he said. Prions,
> the pathogen thought to cause mad cow disease, tend to concentrate in
> a region of the brain called the obex, so the different outcomes of
> the different tests could be due to sampling a brain region that
> contains little or no prions.
> This could be made worse if the animal had lay dead for several days
> before its brain was collected. The brain might be so degraded that it
> would be difficult to locate the obex region for confirmatory testing
> and a sample might mistakenly be taken from a region that contains no
> "So with these samples, the confirmatory testing would be even less
> reliable, not because of the confirmatory test itself, but because of
> the sampling," he said.
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