ELISA [was Re: Bob's Red Mill - a fabulous company]

[Guest guest]

>

> --I just wanted to agree with Heidi. We also love Bob's Red Mill.

> Not only are his products GF, they test them with an test to

> make sure there is no gluten in them

The same test that gives false positives and negatives with CD.

Very reassurring.

If their statement on the Website is correct.

1. Either their testing method is not sensitive enough, which might

mean they are truely GF

2. Or they are still getting contamination up to 20 PPM.

For those who are not clear ELISA = _E_nzyme _L_inked

_I_mmuno_S_orbent _A_ssay. My wife worked on developing this

technology in Japan for forensic analysis. And yet for both her and

my current work we use Radioimmunoassay because has about at 10

fold range of linearity and RIA has effectively a 1000 fold range.

What this means is that values that fall above or below the reliable

colormetric ranges are unreliable. The techique is similar to

photographic development and overexposed parts of the film white out

whereas underexposed areas appear black, the same holds for ELISA.

ELISA is good for crude testing but is not 'stake you life on it'

accurate. For example, I don't use ELISA, I use radioimmunoassay,

even though ELISA would make my work much easier, it would make the

results far less intelligable since one generally does not know the

answer of analysis before on does the analysis. Whereas with ELISA

I would need to run many concentrations of Sera to compare a result

with others seras.

I have refereed many manuscript for publication, this <20 PPM is

ambiguous because it could either mean that their results range from

0 to 20 or that the test they are using is not sensitive below the 20

PPM range. Properly state the result of their testing as you will

find on any bottle of quality chemical is the average value and the

standard deviation. If I am a referee I am to assume that the average

value could be anywhere from 0 PPM to 19.49 PPM. In general when one

sees a greater than or less than value it means that the result is

beyond the ability to test.

Even in the feild of CD studies there are a number of papers that

report the variability of test results by ELISA for the same patients

sera, one of the basic problems is that the colormetric test is

temperature and reagent dependent as it is a colormetric assay. For

example a recent paper out of germany and france reported that the

misdiagnosis frequency between laboratories could vary greatly. Many

people here have some experience with that. ELISA is not definative,

it is more or less a relative test that requires good

standardization. Many people who have used it complain about

the 'edge' effect, for those samples lying on the edge row of a plate

have different values from samples at the center of the plate. Once

again the colormetric character of the assay is the fault. Many

experts, for reasons stated above, disregard ELISA in favor of

mucousal biopsy.

As I said previously I am not singling out a specific company, but

once one starts arguing about crosscontamination of pills or being

kissed by a person who drank a beer one also has to look at

crosscontamination within GF product lines. The recent paper

concerning oats is an excellent example, they found that 2 of the 3

major oat suppliers in the US has wheat berries contaminating the oat

stocks. Since the potential for contamination of a wheat using

company is great, it is up to them to prove that there is not

effective contamination. >20 ppm is not sufficient no matter your

personal feelings about a company.

The target level of gluten is <1mg per week, that roughly is equal

to 1 ppm at 2.2 lbs per week, 0.45 ppm at 5 lbs per week, According

to Bob's Red Mill Website their potential level of contamination

means that an individual could only consume 1/10th of a lb of thier

product a week to be within the targeted range. Liberally considering

that >20 means between 0 and 20 averaging 10 it would mean 2/10ths of

a pound a week. I cannot tell you whether the subject of the paper who

had tenacious CD was typical or atypical, but I have to give a

warning that if a person is really intolerant to gluten, this company

has disclosed that their potential level of crosscontamination is

too high.

If you need I can post aspects of the paper in which this study was

done in gliadin science so that you can see what they are talking

about, yourself. I also suggest you read the NEJM article on wheat

contamination in oats, as some of the GF products may be made from

suppliers of oats that contain also wheat. I took the time the time

to read the packages at the market and now the site carefully, they

did not disclose what measures they have taken to prevent supply line

crossing and supplier contamination.

My opinion is that for a person who has been effectively and fully

treated for CD this level of <20 PPM is safe, but I would not

overconsume this product, but for a person in the recouperative phase

it _might_ be too high to have the product used as a staple in the

diet. In addition I would not consume this product if I have recently

had the flu, gastrointestinal infection of any kind, or prolonged

periods of allergies following cold or flu as during such periods one

is sensitive.