The problems of IGg4 tests
I have also done two new IgG4 tests. As mentioned in blog part 3, I ate a lot of herring before my first IgG4 test. Since I haven’t eaten herring for over 20 years, this should significantly increase my IgG value “herring”, after all, it should be pretty close to “0”. However, as Dr. Kofler – allergy expert at the Allergy Outpatient Clinic in Hall – explained to me, this increase takes six to eight weeks. Therefore, the first test – I assume – was negative directly after eating herring. However, it was questionable whether my experiment would work, as we do not know the standard ranges of the IgG tests and the tests do not give exact values, but work with 6-step scales, the data basis of which is also unknown. But more on that in a moment.
IgG test results
In the first test I had 28 incompatible foods, whereby the different types of milk, cheese etc. do not count, as they all only indicate the IgG value for “casein”. We don’t know why the supplier still offers more than 10 (!) different foods.
Well, I repeated the test after 6 and 8 weeks. With two different providers. Once with the same provider and once with a different one. With the same supplier, there were now 31 incompatible foods, although the incompatible foods have changed slightly. Some were no longer incompatible, others were added. An effect that we are now familiar with from many bloggers, authors and tests. The IgG values can even fluctuate if you do a test on the left index finger and one on the right index finger at the same time1 (9 against 38 intolerances!). Yes, these tests are that reliable …
Even if one assumes, for the sake of fun, that the IgG tests work as advertised, such a result should give one pause for thought …
My “intestinal permeability” remained unchanged (despite taking probiotics, which was recommended to me by the provider to improve permeability). The herring was negative. That surprised me, but didn’t worry me yet, because it can take longer for IgG levels to rise.
With the second provider, tested after 8 weeks, I “only” reacted to 10 foods, whereby this provider summarized the individual types of milk, cheese, etc. under one item “casein” in an exemplary manner. In contrast to the first provider, he has also combined the various fish and seafood (cod, Alaska pollack, salmon, tuna, shrimp) under one item. Uh-huh… Wait a minute! What’s going on?
Herring is not tested at all
This means that the first supplier here (again, as with casein) artificially pushes up the number of foods. You can probably only measure a “fish protein”, but not “herring”, “salmon” or “cod” individually.
But this also means that my herring test cannot work. Why? Well, I haven’t eaten many of these fish for many years. Salmon, pollack and maybe the occasional shrimp. This means that my “herring” value (actually “fish value”) was not 0 at all before the provocation, it was somewhere in the “normal range”. And of course it still is.
Exact values are missing
Presumably my “fish IgG” increased as a result of the provocation, but was still within the laboratory’s “normal range”. In order to measure the increase in fish IgG, the exact IgG value would have to be measured as an actual value, not as a composite value of six bars on an unknown scale. And you need to know the standard ranges. These normal ranges would of course have to be determined separately for each food and each cultural group, since the normal range of a culturally frequently consumed food is higher than that of foods that are rarely consumed. In Central Europe, the fish IgG value should be lower than the gluten or casein value. In Asia, it would probably be the other way around.
So I ask the two providers of IgG tests whether such standard ranges and the corresponding scientific literature exist. After all, I want to be able to interpret my results. I only get an answer from one provider.
The answer from the provider
But the answer is very disappointing. I only learn that the 6-step scale is adopted by the partner laboratory. I am told that “the allergen quantities used for testing are optimized so that the 6-class classification applies to all tested allergens”. This means that the standard ranges are not food-specific. So, assuming again that IgG4 tests actually work as intended, this would mean that the tests are not specific enough and therefore could not provide clinically relevant data.
Because this is an important point, let me clarify once again: even if we assume that IgG4 levels for food intolerances could actually be used to find food intolerances, the self-tests in their current form would not be able to provide results that are suitable for diagnosis. This would require food-specific and culture-specific standard ranges as well as exact IgG4 quantity measurements.
Regarding my question about literature that would prove the 6-level scale, I get a list of about 30 articles! I take the trouble to look through all the publications. None (!) of the publications answers my question.
In accordance with journalistic due diligence, I summarize my findings and ask the manufacturer again. This time I don’t get an answer. In this case, no answer is also an answer.
IgG testing: What remains?
IgG4 tests are not a useful test option for food intolerances. The result is simply not meaningful. No matter how you look at it, no matter how many eyes you turn, even if you give the tests advance praise, the result cannot provide a diagnosis. I have really tried to approach the subject openly and without prejudice, I have made concessions to the tests in thought experiments and even then, no clinically relevant diagnoses would be possible.
What remains with all home tests, from stool to blood tests for home use, is the pale taste of the business practices of some manufacturers, the desire of those affected for a simple miracle test that improves their own lives and, above all, the business with the health of desperate people who may have had bad experiences with conventional doctors or our health system.