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Comment by gcanyon | Hacker News Reader

Not because of an MRI, but this happened to me:

   1. I had a chest x-ray
   2. It showed a small dark patch, and my lungs over-inflate.
   3. Erring on the side of caution, doctor ordered a lung biopsy.
   4. Lung biopsy is painful, annoying, expensive, and non-zero-risk.
   5. Lung biopsy turns up nothing. "Maybe you aspirated some food?" We learn nothing.

N=1, but that biopsy should not have happened.

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I don’t understand how you’re concluding that the biopsy shouldn’t have happened from that anecdote? Just because a test result is negative doesn’t mean that it shouldn’t have happened. That’s not how practicing medicine works.

Hence the N=1 I started the statement with. If we had a thousand similar situations and it turned out that in, say, 1% of cases there was a lung tumor, then we could debate whether it's worth putting 990 people through a biopsy they don't need so 10 can find out they have a tumor. Maybe that gives us the opportunity to discuss waiting a month and taking another chest x-ray (which has its own negatives) vs. doing an immediate biopsy.

But we don't have 1000 similar cases. As I said, we have 1: mine. And it turned out negative. So 1 person was put through a biopsy they didn't need, and 0 people found out they have a tumor.

Hopefully that makes my point clearer.

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