RAST results

The results of Georgia's blood work came in and are as follows: (I'll explain the "Class" numbers to the best of my ability at the bottom of this post.)

Peanut went up but remains at a Class III.
Sesame went up and rose from a Class II to a Class III.

For some of the fish, we were able to get more specific results than in the past. They were able to separately test for cod fish, tuna, salmon, halibut and tilapia, and I'm not sure they did that before because I don't have 2008 and 2009 numbers for all those fish. She's testing positive for all of those. Her cod fish and tilapia scores went down, although they both remain in the Class III range.

Similarly, we got a more specific breakdown of the tree nut scores this year. The good news is that for some of the nuts (i.e., almonds, pine nuts and hazel nuts) her scores are so low that they are considered a Class 0 (i.e., negative test result) or Class I. Our allergist explained this to mean that if Georgia's scores remain low, then when Georgia gets a little bigger the allergist will recommend that she do a food challenge for those nuts. Now, even if she were to pass such a food challenge, she might have to continue avoiding those nuts for fear of cross contamination. However, manufacturing practices are improving, as is allergy awareness, so I know there are already certain products out there (e.g., particular brands of almond butter) that you can safely consume even if you're allergic to other nuts. So, no change on our nut avoidance practices for now, but maybe in a year or two? Fingers crossed.

Her highest tree nut scores were for pecans and walnuts.

Now the grand finale: Georgia's not allergic to shellfish! (Or "sellfish" as she likes to pronounce it.) Woo hoo! As the results have been explained to me, Georgia may never have been allergic to shellfish, but we were previously told to avoid all shellfish due to (1) her allergic history/profile; (2) the fact that testing is not 100% reliable; and (3) the fact that she has a fish allergy, thus making the risk of cross contamination high (due to the handling/processing of seafood). Anyway, we are thrilled. I don't know any 3 year olds who eat tons of shrimp and crab, but I don't care - this still opens up a whole new category of protein for us and moves a few foods back out of the "threat" column for our family. Even if Georgia hates the taste of shellfish, or refuses to eat it, at least Joe and I can now eat crab and shrimp at home without worrying - yea!

Practically speaking, we will be reading labels carefully, and probably buying exclusively frozen shellfish to eat at home. The risk of cross contamination from other fish in restaurants or from the fresh seafood counter at the grocery store is too high to risk eating that stuff.

While I had the allergist on the phone I also picked her brain about DHA fortified foods. You may have noticed your milk or other foods being marketed as, "Now with DHA!" They want you to believe it will make you smarter or make you live longer - I don't know. Hey, I'm not knocking it - I take a fish oil pill everyday hoping there's at least some value to it. What I was worried about was that these DHA fortified products may contain a fish oil that Georgia's allergic to. The allergist's answer was that many DHA products are actually made from seaweed and should be okay, but that we should always read labels. If something's made with fish, it is required by law to state that it includes fish. So, I'll be doing some label perusing at the grocery store soon. Last thing I need is for Georgia to be served supposedly safe milk and cookies, only to find out that the food scientists of the world have figured out a way to get fish into them.

Oh - so a word about the "Class" levels referred to above. In my own words: the Class just corresponds to the level of probability that a positive result is in fact accurate. It is not a measure of the "severity" of one's allergy, though you will see many confused parents discussing these things online as if that is the case. (In looking into the meaning of the Classes, I was amazed at the misinformation swirling around on online message boards. People saying things like, "My son scored a 6 on a scale from 1 to 4." What? That doesn't even make sense. Made me think of Spinal Tap, though - turn it to ELEVEN.) : )

Here's a slightly more scientific explanation from a website called Food Allergy Support, though I have to add that I'm not really familiar with the site or that organization and therefore can't vouch for the veracity of the following:

"The severity of a person's allergic response is not related to RAST level. Class 3 individuals can have severe responses and Class 6 can have mild. RAST tests are only useful to determine whether an individual is allergy, not how allergic they are. However, different antigens have different threshold levels above which an allergic response is likely. For example, people with a peanut RAST result of >14kU/l are likely to have an allergic response to peanut. Soybean typically required >30kU/l; egg as little as 7kU/l. Class 1 and Class 2 often fall below the threshold where most individuals would experience a food reaction, so doctors often consider results in this range equivocal. If results fall in this range and the patient has not experienced an actual reaction to a food, the allergy may be confirmed via a food challenge."

So, there you have it! This was supposed to be a quickie post. Oops.

Allergist Update: RAST Results

The allergist called with Georgia's RAST test results today - woo-hoo! Information!

(Bummer that I was not home and Joe answered the phone, because I wanted to hear it all first hand. I was like, "Tell me everything they said, verbatim! Every word. Did you take notes?" I'm a dork, I know.)

Anyway, great news:

• Georgia's RAST score for egg is low enough that she is now eligible to do a supervised egg challenge in the doctor's office. If she passes the egg challenge, she'll be cleared to eat eggs!
• Her poppy seed and chick pea scores are low enough that we are allowed to try re-introducing those foods to her at home. On the subject of poppy seed allergy: interestingly, an email that I had written to the allergist at the time of Georgia's supposed poppy seed reaction revealed that she had also been eating fish at that meal. (She used to tolerate fish but started having allergic reactions to it within the last year.) So, it is now believed that what I thought was a poppy seed reaction at the time, (since in my mind it couldn't have been the fish, since she'd eaten it many times before with no problems), was actually a reaction to the salmon that she had been eating.

Her peanut, tree nut, sesame and fish scores are all still too high for her to do food challenges on those. Maybe next year.... Fingers crossed that the scores will keep coming down.

So, if we assume for the sake of argument that Georgia is able to pass the egg challenge and successfully reintroduce poppy seeds and chick peas to her diet, then that means our list will go from:

Peanuts and tree nuts, sesame, fish, shellfish, poppy seeds, chick peas, and eggs

-down to-

Peanuts and tree nuts, sesame, fish and shellfish

(Which for the sake of simplicity could be summed up as: Nuts, Sesame, Fish. Doesn't that sound like a MUCH shorter list than what we have been dealing with? I think so.)

All in all, a great report.

More Waiting...

Well, things went fine at the allergist, but the appointment was a bit anticlimactic.

I know, I'm an idiot, because what was I expecting? The whole mystery to be solved?

Anyway, I thought they'd be doing skin testing again, but it was just blood (RAST) testing, which means that we'll have to wait about a week for the results.

Blood Test Results from Food Allergy Study

They told us it would take about 2 months to get back the blood test results from our participation in the food allergy study, and they were true to their word.

This is science-y stuff, so I'm not even going to attempt to summarize or paraphrase. I'm just typing in excerpts of what they mailed us now:

Interpretation of Blood Test Results

...The purpose of this testing is for an epidemiologic study and not for diagnosis.

IgE is the antibody that causes immediate hypersensitivity to proteins, such as foods or airborne allergens. The total IgE value is a general indicator of how "allergic" a patient is. For example, patients with hay fever (allergic rhinitis) or eczema (atopic dermatitis) may have an elevated IgE level. For total IgE, the lower limit of detection is 2.0kU/L and the upper limit is 5000 kU/L.

The blood tests called "CAP-RASTs" determine the quantity of IgE to a specific allergen. For specific IgE, the lower limit of detection is 0.1 kUA/L., and the upper limit is 100 kUA/L.. Values outside this range will be noted as "<0.1>100 kUA/L." Please note that CAP-RASTs, especially to foods, can be falsely positive. The main limitation of these tests is that a positive result does NOT necessarily mean that the food will trigger symptoms...

POSITIVE BLOOD TEST ALONE DOES NOT EQUAL DIAGNOSIS OF ALLERGY

Sometimes, CAP-RASTs can also lead to false-negative results (although a negative test result generally rules out an allergy)...

In addition, the blood test results do not reflect the severity of an allergy. A higher value does not mean that a reaction will be more severe. Rather, the value reflects the probability that you or your child may be allergic to that particular allergen: the higher the value, the more likely that the result is a true positive....

	Mother	Father	Daughter
Allergen tested	Value (kU/L)	Value (kU/L)	Value (kU/L)
Alternaria (mold)	<0.1	1.300	<0.1
Cat Dander	<0.1	<0.1	0.417
Cockroach	0.143	<0.1	0.102
Codfish	<0.1	<0.1	20.871
Dog Dander	<0.1	<0.1	0.110
Dust Mite 1 (Df)	<0.1	1.397	<0.1
Dust Mite 2 (Dp)	<0.1	0.872	<0.1
Egg White	<0.1	<0.1	0.887
Milk, Cow	<0.1	<0.1	0.672
Peanut	<0.1	<0.1	4.182
Sesame	<0.1	<0.1	6.615
Shrimp	0.236	<0.1	<0.1
Soy	<0.1	<0.1	1.148
Total IgE	16.151	23.727	108.137
Walnut	<0.1	<0.1	6.049
Wheat	<0.1	<0.1	4.020

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Okay - me here again. So, my thoughts on what we can take away from any of this:

--One more thing to keep in mind when looking at these results - you can't compare CAP-RAST scores for different allergens and infer that equivalent scores mean equivalent likelihood of being allergic (i.e., true positives). In other words, a 4.0 on peanut may not mean the same thing as a 4.0 on wheat.

--Obviously, we'll have to wait to get in to see the doc this fall for further testing and discussion, but Georgia's egg test result confirms my suspicion that she may have outgrown this allergy. I don't really know how to judge it, but that number looks low to me! I believe it's lower than her score from 2008, which is great news.

--Definitely true what they say about false positives, because I eat shrimp with no problems, and Georgia consumes milk, wheat and soy with no problems as far as we can tell.

--Based on what little I know of Peanut CAP-RAST scores, I am pleased with Georgia's score on that one. It's definitely well below the 95% certainty threshhold. It may indicate that even if she's allergic now that she's among the 20% of people who have a decent chance of outgrowing a peanut allergy.

--Bummer about the codfish score for Georgia. Her reactions to fish started around February or March, which was so weird, because she had been eating salmon with no problem and loving it for about 6 months prior to that. I wonder if or when we can find out which fish she's allergic to? We'll have to ask the doctor about that. I hope she doesn't have to avoid ALL fish forever.

"Being Treated as Allergic" vs. "Allergic" (and also: why I'm not convinced Georgia's allergic to eggs)

Okay, this is a subject that is still confusing to me.

Medical testing for food allergies is notoriously inaccurate in that it gives a lot of false positives. So, if someone gets a positive skin or blood test, how do you know if it's an indicator of a true allergy or just a false positive? Well, you rely on whether the person has had a reaction to actually ingesting that food. If so, then you can feel confident that the positive test result is accurate. If not, then there's a very good chance that it was a false positive.

Fine, but what about if the person hasn't ever even tried the food in question? Seems you might just feed it to them to find out if they're allergic, but it's not that simple because that can be quite risky. My understanding is that they (the doctors) look at a couple of factors: (a) the age of the patient, and (b) the numeric result of the RAST (blood) test.

Age of Patient: I could have this wrong, but I think that in some cases, based on the age of the patient alone, the doctors will not proceed with a food challenge or suggest that the child eat the food, because it is safer to just wait and have the patient re-tested in a year. Whether a food challenge may be in order is something that gets considered when the child is a little bit older.

Numeric Result of the RAST test: For whatever reason, each food has a different scale on the RAST test - (this is what I've been told, anyway). So, maybe egg ranges from 0 to 10, but peanut ranges from 0 to 15, and apple ranges from 0 to 12, or something like that. (I am making these numbers up, they may be more like 0-100, but that's not important.) The score on the RAST test is not considered to be an indicator of the severity of the allergy. You could score a 1 for peanut, and so long as it's a true positive and not a false positive, you may have the same allergic reaction to peanuts as someone scoring a 15 on the peanut scale. However, the score on the RAST test is believed to correlate with the degree of reliability of a positive result. So, for instance, if someone scores a 14 on the peanut scale, maybe that means the doctor is 95% certain that that's a true positive rather than a false positive, whereas if someone scores an 8 on the peanut scale the doctor may feel that there's only a 70% chance that that's a true positive. (Again - I am making up the numbers here just to get down the general concept.)

What a mess, right? Because in the end, even though the degree of certainty from the test results varies depending on the person's score, the person who scored an 8 (or a 1 or whatever for that matter) might very well actually be allergic to the food in question.

So, bringing this all back to Georgia....
In her case, she scored just barely high enough on the RAST test for eggs that the doctor did not feel comfortable letting us do a food challenge for eggs. In other words, her numeric score gave the doctor just enough certainty that the positive result was a true positive that she doesn't want to chance a bad reaction by feeding Georgia any eggs. So, we have been instructed to eliminate all eggs from Georgia's diet and are following the doctor's orders on this.

I have my doubts that Georgia is actually allergic to eggs. Maybe that is wrong of me to say, but I am just being honest. I say this because of 3 things: (a) prior to allergy testing, she had previously eaten cooked egg yolks without any observable reaction [granted, it is the protein in the egg whites, not the yolks, that people are allergic to, but given that we had separated these eggs by hand prior to cooking the yolks for her, I somehow doubt we actually removed every single egg white particle perfectly in the process of separating, so she probably ate some, right?], (b) she had birthday cake when she turned 1 without any observable reaction [although, admittedly, there are studies out there showing that some people with egg allergy can tolerate eggs cooked at very high temperatures - like in baked goods], and (c) the fact that her RAST blood test result for egg was just barely high enough for us to miss the cutoff point at which the doctor would've considered her eligible for a food challenge for eggs. So, I could be wrong, obviously, but I'm just being honest and saying that in my heart of hearts I do not think that Georgia is actually allergic to eggs. My hope is that when we go back in the fall of '09 for additional testing that Georgia will test even lower on the RAST test for eggs and will be cleared for a food challenge, and that my doubts of her egg allergy will be proven correct, (or, if she is actually allergic to eggs now that she will have outgrown the allergy). All of this said, we are not idiots and are therefore following the doctor's orders to a T. We do not feed her any eggs. We describe her to others as allergic to eggs and expect them to treat her accordingly - because the doctor has told us that she is - simple as that.

Anyway....getting back to the whole testing thing....
Georgia was not tested for poppy seed allergy when we had her tested for allergies in the fall of '08 (good Lord, why would she be? poppy seeds, for cryin' out loud?!), but several months later she later had a reaction to poppy seeds, so I had to call the allergist about that. During this phone call I asked a few more questions about the testing and got some clarification. My question was basically: "Is Georgia allergic to peanuts? Because I know she tested positive for those, but she has never eaten them, so how do we know?" (i.e., how do we know that these weren't false positive results?)

Answer (paraphrasing here, obviously): She scored an 8.19 on the RAST test for peanuts. At this level, judging only from the RAST results, (since she hasn't eaten any peanuts yet (except via breastmilk) or had any known reaction to peanuts), it is "probable but not certain" that she is allergic to peanuts. Her RAST score does not put her into a category where we could say with above 95% certainty that she is allergic to peanuts. But based on the probability that she is allergic, we are advising you to delay introduction of peanuts to her diet. If, one day, she is able to score below a 5 on the RAST test for peanuts, and she is at that point over 3 years of age, then we will probably do a food challenge for peanuts to find out for sure. Until those criteria have been met, it would be too risky to do a food challenge. (Peanuts being notorious for causing the most severe of reactions, like anaphylaxis, in those who are allergic.)

So, to sum up: since Georgia has never eaten a peanut (except via breastmilk) or had a known reaction to eating a peanut, the allergist might technically say that Georgia is "being treated as allergic" to peanuts rather than saying that she is certain that Georgia "is allergic" to peanuts. But from a practical standpoint, this is a distinction with no meaning. Either way, the point is that she can't eat anything with peanuts. So everyone, including the allergist, would/should just call her "allergic to peanuts" for simplicity's sake until it's been proven otherwise, (which unfortunately, it sounds like we can't even hope for happening until she's at least 3 years old).

EDITED 8/12/09 TO ADD: Since writing this post, I've learned a little bit more about the RAST testing, and I don't think I explained it quite right here. My understanding is that the scale is the same for each food, it's just that for each food there is a different point at which the doctors will say with 95% certainty that you are allergic to that food. So, for instance, a score of 4.5 for shellfish and a score of 4.5 for peanuts may not mean the same thing as far as the chances that each result is a "true" positive. This post from 8/8/09 explains it a little better, I think.