To those of you just joining us, I recently stirred up a hornet’s nest by writing on the alleged link between autism and vaccines. Since then, I’ve gotten a crash course in the subject, from a few friends, and now, a reader and a writer in his own right, Robert Hinkley. Mr. Hinkley writes to debunk some of Kirby’s claims that were made at a lecture in London earlier this month. I’ll reproduce his e-mail, edited for inline links and pictures, but nothing else, below. Be warned that some of his links are down: server problems.
I went to David Kirby’s lecture in London a week ago (I wrote about it here) and would like to tip you off to a couple of slides he used in his presentation then, in case he uses them when he speaks at NYU School of Law on the 26th. Kirby presents the slides as supporting his mercury/thimerosal/vaccines-cause-autism case, but in reality they do nothing of the sort. I thought I’d mention them to you in case you do manage to go along, as Kirby throws out a huge
volume of stuff and it might help to be prepared about a couple of specific things he says.
One slide he uses (see ‘chelate-result.jpg’, right) shows the results of an analysis of the urine of an autistic child, showing levels of mercury far higher than those found “within the reference range”, ie what would be expected in the urine of a healthy person who hadn’t suffered mercury poisoning. Kirby presents this as evidence that the child’s body had retained unusually high amounts of mercury, thus they’d been poisoned by mercury and their problems could be a result of their unusually high burden of mercury. This actually produced murmurings of amazement in the London audience and it does seem very compelling. The truth, however, is different. The urine was analysed after the child had been given a chelating agent: a drug specifically designed to cause their body to excrete the heavy metals it contains. But the reference concentrations for the amount of expected mercury in the urine are for urine from people who haven’t been given a chelating agent. Anyone givena chelating agent would be perfectly expected to produce urine with levels of mercury higher than those normally found in the urine of people who haven’t been given a chelating agent. The use of such “provoked” urine tests being compared to “unprovoked” reference results is explained better than I can do it by Steven Novella here. I also guess Kirby’s not aware of the 2007 paper published in ‘Clinical Toxicology’ which found that autistic children didn’t generally excrete higher levels of mercury (or arsenic, or cadmium, or lead) than non-autistic children (see here). That paper is of course a preliminary pilot and the number of subjects is low, but it certainly shows that not all autistic children exrete large amounts of mercury.
Another slide (see ‘denmark.jpg’, right) shows autism diagnosis rates in Denmark before and after the removal of thimerosal from childhood vaccines. Kirby says that people use this (autism rates apparently increasing after removal of thimerosal) as evidence against a thimerosal-vaccine link but claims they are wrong to do so. Kirby says that before 1994 the Danish healthcare system was only diagnosing a small proportion of autism cases (13% was the figure he gave), so the autism rates recorded pre-1994 were artificially low. Leave aside for a moment the fact that Kirby is willing to embrace the notion of different diagnostic methods producing an apparent rise in autism in Denmark while denying it can have happened anywhere else. If you multiply the diagnosed pre-1994 autism rates by 8 to approximate Kirby’s claimed “true” rate you still get cases of autism – at least before 1990 – lower than they are in the late 1990s after the removal of thimerosal from childhood vaccines.
As Hinkley indicates, you can probably expect more information on his own site soon. I’ll link to it when it comes up.