Your doctor recommends a test or treatment, clearly with the intent to help you.  But how do you know how likely it is that it actually will help you?  And how likely is it that side effects or complications will outweigh the possible benefits?

In most cases, science hasn’t reached the point where it can predict exactly who will benefit from a given treatment and who will not.  However, it is possible to say how many people out of 100 are typically helped and how many are harmed by the treatment.

You can see this information for 100+ treatments at http://www.thennt.com/home-nnt/.  (NNT or “number needed to treat,” is the number of people who must be given a specific treatment in order for one person to benefit.)

Be aware that the site is run by doctors.  They tend to talk in doctor-speak.  For example, one treatment listed is “Anticoagulation given for acute venous thromboembolism (deep venous thrombosis and pulmonary embolism).”  To non-medical people, this means “blood-thinners given to treat people with blood clots.”

If you can make your way through the medical jargon, you can find information that can help you decide whether the probable benefits of a proposed treatment are valuable enough to you to outweigh the probable risks.

For example, the doctors analyzed studies of statin drugs given to people for five years to prevent heart disease, when the people weren’t already believed to have heart disease.  The doctors concluded that 98% of the people saw no benefit, 1.6% were helped by having a heart attack prevented and 0.4% were helped by having a stroke prevented. 

However, they also concluded that 1.5% of the people were harmed because they developed diabetes as a side effect of the drug, and 10% were harmed by muscle damage. 

The NNT website put this treatment into their “red” category, meaning that they concluded that “the benefits don’t outweigh the harms.” 

You or your doctors might know something about your medical situation that could lead you to decide that you want the treatment anyway – but at least if you had this information, you would know the odds that you were up against.

Treatments on the NNT site may be rated green, yellow, or red – or even black, in cases where treatments “have very clear associated harms to patients without any recognizable benefit.”

Another website reports the results of careful evaluation of the benefits vs. the risks of preventive measures such as screening tests, immunizations and preventive medicines.  Run by the U.S. Preventive Services Task Force, the site found at http://www.uspreventiveservicestaskforce.org/recommendations.htmoffers a searchable list of topics in alphabetical order, as well as separate summaries of its recommendations for preventive services for adults and for children.

This site grades its recommendations from A to D, with “A” meaning that the task force recommends the preventive service because “there is high certainty that the net benefit is substantial.”  A grade of “D” means that they recommend against the service because “there is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits.”

They also rate some screening services an “I” for “insufficient,” which means that they have concluded that there just isn’t enough good data to draw a meaningful conclusion about whether the preventive service helps more than it hurts.

Comparing the trade-offs at either site requires some thought.

For example, the NNT site evaluated CT scanning to screen for lung cancer in people at high risk of developing the disease.  They rated this service “yellow,” meaning that they don’t think the data is clear about whether the benefits outweigh the risks.

They report that 99.5% of people got no benefit from the scan, but the scan saved the lives of 0.5% of the people.  On the other hand, 23% of the people tested were harmed by being told that they had lung cancer when they didn’t; these mistaken results are termed “false positives.” Further, 3.5% were harmed by having an unnecessary operation due to a false positive.  And 0.6% were harmed as a result of a complication of surgery.

If you were at high risk for lung cancer, would you want this test?