Some medical conditions aren't easily diagnosed with an X-ray, CT scan, or MRI. Carpal tunnel syndrome (CTS) is one of those problems. Sometimes it's caused by a medical condition such as a tumor, hormone imbalance, liver disease, or diabetes.

Once the doctor has ruled out a medical cause, it's time to look at posture, nerves, or muscles as the possible cause. Again, problems with these variables don't show up on imaging studies. Nerves can be tested using nerve conduction studies. Muscles can be tested with electromyography. Both of these tests can be uncomfortable and expensive.

In general, the rising costs of health care have pushed researchers to find ways to predict who's at risk for CTS. The next step is to reduce the risk by eliminating as many of the risk factors as possible.

A second step involves using a clinical prediction rule (CPR). Researchers help doctors find out which tests used in the clinic are the most reliable and accurate. There may be a CPR for each disease, illness, and condition. There may be one best test or a group of tests that give an accurate prediction.

You may have endured a variety of tests because a clear CPR for CTS isn't available yet. The first study on this topic was reported this year (2005). More studies will be done to verify the results.