People have become far more sophisticated when making purchases these days. One of the first things they check is the reviews from other shoppers. How many are there, and how well did the product perform?

Objective resources are also helpful. For example, Consumer Reports is a nonprofit organization that does its own thorough testing.

If you have used Consumer Reports for your own shopping decisions, you know that the information is presented in easy-to-understand tables. There is a lot of information crammed into them. In one recent review of air filters, there were 18 columns of data.

Of course, CR is especially renowned for its car reviews. Each vehicle is rated with a number so you can easily compare one model to another. They also analyze a wide range of criteria, from acceleration and braking to predicted reliability and overall miles per gallon.

Wouldn’t you like to be able to assess your prescription medicines with a similar data grid? Most physicians and patients have no idea how effective one medicine might be compared to another. Rarely are people told how likely they are to experience a side effect.

We continue to be disappointed that health care professionals and their patients don’t seem to demand this kind of information about something so important.

They can get more detailed information about a toaster they might buy than they can about a proposed blood pressure medicine or cholesterol-lowering drug.

That brings us to an underappreciated indicator of drug effectiveness. We would hope that every time a patient gets a new prescription, they would be told the “number needed to treat” or NNT. This number describes how many people would need to take a medication for one person to overcome the health problem they are trying to treat.

For the NNT, lower is better. If an antibiotic had an NNT of 1 for clearing a staph infection, it would mean that it worked for every patient. We don’t know of any medicines that effective.

In fact, people may be surprised at just how high the NNT is for some very popular medications.

If you look at cholesterol-lowering drugs for people without heart disease, you will find that for avoiding a heart attack, the NNT is 104. In other words, more than 100 relatively healthy people would need to take a statin for five years for one to avoid a heart attack. That is a lot of people taking a medication for one person to avoid a heart attack.

Drug companies recognize that a 1% chance of benefit is not impressive. That is why they much prefer to cite “relative risk reductions.” The maker of Lipitor (atorvastatin) used to advertise that its cholesterol-lowering drug reduced the risk for a heart attack by 36%. That seems impressive until you notice the asterisk next to that number.

If someone followed the asterisk, they would read: “That means in a large clinical study, 3% of patients taking a sugar pill or placebo had a heart attack compared to 2% of patients taking Lipitor.” In other words, one person out of 100 could avoid a heart attack after five years.

That is why patients deserve to know the NNT for every medicine that is prescribed. Until both prescribers and patients adopt an objective measure of drug effectiveness, people won’t be able to make informed decisions.

In their column, Joe and Teresa Graedon answer letters from readers. Write to them in care of King Features, 300 W. 57th St., 41st Floor, New York, NY 10019, or email them via their website: www.PeoplesPharmacy.com. Their newest book is “Top Screwups Doctors Make and How to Avoid Them.”