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Morendil comments on How to Evaluate Data? - Less Wrong Discussion

5 Post author: jetm 09 April 2013 04:10AM

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Comment author: Morendil 10 April 2013 01:52:37PM *  15 points [-]

Overall the contents of the linked page make me want to update quite a bit away from trusting MetaMed. One more example:

One million children every year have had unnecessary CT scans, which risks exposing them to radiation levels up to those experienced by survivors of Hiroshima and Nagasaki.

Compare with this excerpt from the primary source, which presumably serves as the basis for the claim:

Most of the quantitative information that we have regarding the risks of radiation-induced cancer comes from studies of survivors of the atomic bombs dropped on Japan in 1945. Data from cohorts of these survivors are generally used as the basis for predicting radiation-related risks in a population because the cohorts are large and have been intensively studied over a period of many decades, they were not selected for disease, all age groups are covered, and a substantial subcohort of about 25,000 survivors received radiation doses similar to those of concern here — that is, less than 50 mSv.

The primary source is not claiming that "a CT scan exposes you to Hiroshima-Nagasaki survivor radiation levels". It is saying the converse - "some atomic bomb survivors received doses low enough to be comparable to CT scans". The phrase "survivors of Hiroshima and Nagasaki" is pure fear-mongering - how much radiation the typical atomic bomb received is not public knowledge, so we'll tend to think in terms of worst cases (this handy chart might help). The average dose received, however, was 210 mSV according to one source I consulted; this is four times the high end dose from a pediatric CT, with the low end around 5 mSV. The statement from MetaMed is perhaps not an outright lie but it is at least grossly misleading.

For a business which has been touted right here and by no less than Eliezer himself as providing "actual evidence-based healthcare", this is a little worrisome.

(ETA: contrary to appearances I'm not actually trying to take over this whole post's discussion area, but I happen to get easily nerd-sniped by fact-checking exercises and easily worked up when I get a sense that someone is trying to pull a fast one on me.)

Comment author: private_messaging 26 April 2013 10:49:44AM *  5 points [-]

Alternatives in medicine are primarily a domain of crackpots and scam artists, and it is of no surprise what so ever for me that the individuals involved in this sort of thing would capitalize on fear of radiation.

The doses are highly misleading; the CT scan is typically not a whole body exposure, and the cancer risk is proportional to tissue-adjusted whole body exposure not the organ doses. Which, for the CT scan of the head, is 1..2 mSv . The annual dose from all sources is listed as 2.4 mSv in US .

While there's little question (based on our understanding of cancer and radiation) that the risk continues linearly at arbitrarily low doses, the risk of 1..2 mSv exposure is small and is utterly dwarfed by the risks inherent in ordering some non domain expert medical advice over internet. Especially considering that there are guidelines for when to do and not to do CT scans, compiled by experts who work on this specific issue for far longer time, and considering that there are considerable risks involved in not doing a CT scan.

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