It depends on what the definition of "leads to" is
Charles Krauthammer is being deceptive as usual.
"What did he suggest to address the plague of defensive medicine that a Massachusetts Medical Society study showed leads to about 25 percent of doctor referrals, tests and procedures being done for no medical reason."
There are two interpretations of that sentence. One is that he claimed that the Massachusetts Medical Society demonstrated that all (100%, 13 out of 13, 17 out of 17) un-necessary referals, tests and procedures are due to defensive medicine.
This can't possibly have been shown. Also it is not conceivable. Doctors are human and they make mistakes for reasons other than fear of malpractice suits.
Or did he just claim that 25% of referals etc were shown to be un-necessary and asserted that defensive medicine has something to do with that. That without defensive medicine it would be maybe 24%.
For that matter, maybe 26%. It could be the effect of fear of malpractice suits is that there are fewer un-necessary procedures because some doctors are afraid of being sued when un-necessary procedures have adverse consequences.
I mean defensive procedures ? How many physicians have been sued for not performing a procedure ?
Doesn't the similarity of the estimates for referals and tests on the one hand and procedures on the other provide near proof that fear of malpractice suits is not a major factor ?
So what does he assert is the fraction of procedures that are -necessary procedures caused by defensive medicine ? It could be 25% or 1% or -1%. You consider the number 25% definitely an estimate of the effect of defensive medicine. I think you fell for his trick.
I just re-read my opening sentence and I wish to retract the claim. I can't be confident it is true. I said he is usually deceptive. That implies that I can think of an honest argument made by Charles Krauthammer. None comes to mind, so I can't rule out the possibility that he is always deceptive. I apologize for my careless wording, which is inexcusable in a comment which contains the numbers 100% etc. I couldn't swear that I know that Krauthammer is deceptive less than 100% of the time.