‘Number Needed to Treat:’ a clear way to figure whether care’s effective

Modern medicine can get mired in a lot of mumbo jumbo, so much so that it gets daunting for patients and consumers to try to understand something simple but critical: How effective is a therapy that my doctor wants me to have?

Because I’ve written before about the virtue in a clear and decisive figure, the Number Needed to Treat (NNT), I was delighted to see that Stat, the online health news site, has published a piece headlined, “What are the odds your medication will help you get better?”

The article explains that the NNT answers the question:

How many patients needed to be treated in a certain way for one to benefit?

It describes how the drug to treat red eye (the very common infection  conjunctivitis) has an NNT of 12, meaning, say, a dozen kids who got this fast-spreading bug would need to take the oft-prescribed eye drops before one, who otherwise would have been infected, was helped; the 11 others either would get better on their own or aren’t helped.

Stat notes that the NNT requires sound, deep research to be most effective. But it is remarkably clarifying, explaining, for example, why compression socks (NNT 7) are often doctor-recommended for patients at risk for deep blood clots; the socks are relatively cheap, have low risk of harm, and they work.

The site quotes an expert observing, “an NNT of 5 or less was probably associated with a meaningful health benefit,” while “an NNT of 15 or more was quite certain to be associated with at most a small net health benefit.”

Still, some common therapies have high NNTs, including statins (104 for heart attack, 154 for stroke) and aspirin (1,667 for healthy people and stroke or heart attack). The explanations are enlightening, including the information that many physicians don’t seem to consider the NNT in their practice.

Want to learn more? Check out this website devoted to the NNT.