--- title: Use a symptom checker to help decide whether CT scan is necessary description: Use a symptom checker to help decide whether CT scans and other tests are really necessary. --- March 22, 2013 # Use a symptom checker to help decide whether CT scan is necessary USA Today ran a very interesting [article](http://www.usatoday.com/story/news/nation/2013/03/21/ct-scan-concerns/2005729/) yesterday about the benefits and risks of CT scans. The article highlights that the CT scan is a truly wonderful tool which shows amazing detail such as pinpointing the location of a potentially fatal blood clot on the lungs. However, one chest CT scan delivers, for example, about 70 times the radiation of one chest x-ray. It is also estimated that around 1/3 of CT scans ordered are unnecessary. This means that it is really important for patients to understand whether the CT scan their doctor recommends is really necessary. What’s it for and could another test, such as an ultrasound, be as effective. If the doctor is ordering the scan to help them with finding a diagnosis then you, as a patient, need to be clear what diagnosis they are considering. They should be ordering the scan to confirm something they already suspect because of the signs and symptoms that you have and not just in the hope that it might reveal something. You can help check whether the doctor’s thinking makes sense by using a symptom checker to put in your symptoms and see which diagnoses appear as strong possibilities. You should make sure that your doctor has thought about some probable diagnoses and that he has a ‘differential diagnosis’ (list of probable diagnoses for you the patient) that he is considering. You should then satisfy yourself that his differential diagnosis matches or makes sense with the list you have obtained from the symptom checker. If, for example, your doctor has not considered any of the top 10 suggestions in the Isabel symptom checker list but had ordered a CT scan (or any test) for something that is only in the bottom 10 suggestions or not even on the list, then you should seriously question why that scan or test is being ordered. The symptom checker is a powerful tool that gives the patient the ability to form their own judgement as to whether a scan or any test being ordered by their doctor makes sense. Just because lots of tests are being ordered doesn’t mean you, the patient, are getting good care. 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