Dear Holle,
When I had arthritis I totally disregarded the ALCAT test as valid because of some of the same types of webpages you found. The Allergy Society of South Africa and one from New Zealand and Australia have official sounding pages that look well researched and sound well thought out, but their conclusions about the ALCAT test not having value, it turns out to be untrue. I do not know why these groups persist in their slander of the ALCAT test using specious reasoning. I talked to an ALCAT representative who was present at some of the challenge testing done in New Zealand. His story is that his interpretation of the results of the testing and what that group decided to publish as its conclusions about the testing were shockingly different.
It wasn't until I caught a form of neuroinvasive West Nile virus that cause menigitis in me in 2004 and was having trouble recovering in the months afterward that I went to an MD who recommended the ALCAT test for me. I resisted because I had believed such websites as the one you referenced. My MD, however, provided higher quality, more accurate references for me to study. I had the test done. The diet was amazing in its ability to knock out the residual inflammation in my nervous system that was keeping me from healing. I realized she was getting amazing results with her other patients as well. I realized the ALCAT test would have been a godsend, if I had been willing to take it back when I had arthritis. It would have saved me probably two years of fasting and selective reintroduction in order to identify all my problem foods and substances.
Since I have been using it with my clients, I have found the ALCAT test to be extremely valuable in identifying problem foods. In my experience, it has high clinical relevance. If you would like to see some of the medical literature supporting the validity and usefulness of the ALCAT test you can visit:
http://www.alcat.com/clinical_info