New or modified medical tests and treatments are created constantly. Often, though, they end up being used for patients whom they are more likely to hurt than to help. Five examples described below all made the news in a two-month period in 2011.

First, a New York Times article reported that metal-on-metal hip replacements work well for tall, middle-aged men. The article notes, "But, as with many innovations, metal hips were marketed to all comers."

In fact, 65 percent of these devices went to women and the elderly. Those are the patients most likely to suffer "dire consequences" from this treatment, the article states. Metal particles can break off inside the patients' bodies and cause serious harm.

Second, the Washington Post reported that hospital patients sometimes get "double CT scans." That means that they get two CT scans in the same session. The first one is done without contrast dye. The second is done after a contrast solution is injected into the patients' veins.

Experts commented that double CT scans are almost never medically necessary. However, in some hospitals 5-10 percent of the patients who had CT scans received double scans. In one hospital, 89 percent of Medicare patients who had CT scans got double scans.

CT scans deliver about 70 times as much radiation as X-rays do. When people have scans they don't need, they increase their risk for cancer - without getting any health benefit.

Third, a New York Times article described patients who got pacemakers that cost up to $70,000. The pacemaker works for people with a very specific type of heartbeat irregularity. However, it is implanted in many people who don't fit that profile. About 40 percent of the patients got "no benefit at all" from them, the article noted.

Fourth, a Wall Street Journal article reported on elderly patients who had had colonoscopies. This test is used to screen for colon cancer. In people at low risk and whose first test is normal, no benefit to retesting more often than every 10 years has been found.

However, almost a quarter of the patients were retested within seven years. Thus, they were exposed to risks from the test itself without getting any health benefit. For example, in a small number of cases, the doctor accidentally nicks the colon. The patient could need surgery as a result.

Fifth, a New York Times article reported on a study of a drug that helps when people bleed too much during surgery. About 97 percent of the time when it was prescribed, it was for patients who weren't in that situation. Research shows that, for them, "the drug not only fails to improve survival, it increases the likelihood of a blood clot in the heart or brain, resulting in a heart attack or ... stroke."

What's going on here? Why are so many patients prescribed tests or treatments that aren't a good fit for them?

Two obvious explanations spring to mind.

The first is that doctors are happy to have tools in their toolkits that can help patients. They want to offer those same benefits to as many people as possible. They may lose track of the footnotes, so to speak, which warn that the test or treatment is useful only for certain people.

The second explanation is that doctors may make more money by doing more tests and giving more treatments. In fact, many doctors have something in common with factory workers of a hundred years ago in the worst sweatshops. They are often paid piecework.

That is, a factory worker might have been paid a few cents for each widget he assembled or each collar she sewed. The only way to get ahead was to work inhumanly fast and assemble or sew more and more pieces.

Doctors who are self-employed typically are paid for each test or treatment they deliver. To make more money, they may conclude that they need to deliver more tests and treatments. It can be tempting to overdo it. Added to this picture is the fact that doctors often seem to genuinely believe that there are no downsides to medical care, so ordering extra tests or treatments may seem harmless.

This optimistic outlook doesn't match the facts very well. A great deal of research shows that too much care and too little care are both associated with worse health.

What can you do to protect yourself when you are prescribed a major test or treatment?

Ask questions. Besides asking what the purpose of the test or treatment is, how accurate or successful it is, what benefit it will provide, and so forth, it may be useful to try to avoid getting treatments that help a subset of patients that doesn't include you.

You might ask, "What are the characteristics of patients for whom this test or treatment has been shown to provide great results?" "What characteristics do I have that are different from theirs?"

It is helpful to seek answers that are as specific as possible. For example, it is not very helpful to be told, "This treatment is good for people with bad knees." It is better to know, "This treatment helps two-thirds of athletic men aged 30-40 who have had anterior cruciate ligament tears in the preceding three months."

Medical research typically omits patients with more than one medical problem. If you have several medical conditions, it may be useful to ask additional questions.

You might ask, "Is there any research available about what happens to patients when they get this test or treatment, if they have the set of problems I have?" "How might this test or treatment make any of my other problems worse?"

Don't assume that just because a test or treatment exists, it's a good fit for you. It may be a perfect fit for your neighbor and a disastrous one for you.