“Efficacy and effectiveness trials have different goals, use different tools, and generate different messages.” – Porzsolt et al 2015

Since learning the very large difference between Efficacy and Effectiveness, I’ve noticed that the terms are misused absolutely all the time, especially on blogs, news articles and even by experts (who simply aren’t also research experts). They seem to be used interchangeably, and they should not be. They are very different. 

• Efficacy refers to “a biologic effect (which) can be observed under ideal study conditions.”- Porzsolt et al 2015. One example of efficacy in acupuncture research would be a study of the change in blood levels of neurotransmitters when the LI 4 point is stimulated in a very specific way. 
• Effectiveness “means an effect is detected not under ideal but under real-world conditions.” – Porzsolt et al 2015. One example of effectiveness in acupuncture research would be the change in the level of pain reported after a series of individualized acupuncture treatments are given.

Porzsolt et al. state an important point: “The efficacy of an intervention demonstrated under ideal study conditions (explanatory trial) will not necessarily predict the effectiveness of the same intervention described under real-world conditions (pragmatic trial).” This means that just because that LI 4 point (see example above) produced a change in blood levels of neurotransmitters, doesn’t necessarily mean it will make a meaningful difference in the life of the person. This also brings up a discussion on the difference between statistical significance and clinical significance. 

A treatment is said to create statistically significant change when the effect is large enough (and there are enough data points) to show that it likely wasn’t due to chance alone. This is undoubtedly an important measure of the true effect of a treatment, but it isn’t everything! The result of a treatment can be statistically significant, but it may or may not also be clinically significant. Something is clinically significant if it makes a difference in the actual outcome, such as a decreased rate of cesarean births or decrease in the rate of epidurals given during labor.

The key thing to remember is that most (though not all) acupuncture trials measure effectiveness, and should be discussed in such terms. If you hear someone say “The efficacy of acupuncture treatments for lower back pain was studied”, it may be worth looking more closely to determine if they are really talking about effectiveness, and if so, whether this a reliable source of information?