Blood Drug Testing

Whan doctors do blood tests is everything tested or are there specific types of blood tests for every illness?

example: is the same type of blood test used to find pregnancy used for cancer? or is the same type of test used for brain cancer used for lukemia? can something be overlooked?

Public Comments

1. Dr.'s request blood test for specific things, they don't usually ask for the whole gambit available of tests, and they would probably have to draw alot more blood than a few little tubes of blood in order to do that. something can always be overlooked, of course. you have to be open and honest with your Dr about your symptoms...they are not mind readers.
2. There are different TYPES of tests. Brain cancer would most likely use a scan to detect it, but there are blood tests that look for tumor markers, which may or may not be specific for that disease. Leukemia could be found in a blood smear. Even among cancers, there are so many different tumor markers in the blood. Usually a doctor will take a history, do a physical exam, then test for the most likely causes. A pregnancy blood test is for a hormone. Every body system changes blood levels of different chemicals in different ways. Many times it is a combination of different tests which give the diagnosis. Yes, of course sometimes things might not be tested for if they aren't suspected.
3. Specific tests are for specific results, which reveal specific meanings to the Dr. There are various kinds of enzymes that reveal various meanings so while ordering one blood test everything will not be revealed. As regards overlooking something the machines don't overlook anything it only us humans who overlook
4. When you have a blood test the doctor writes down what they want the lab to look for - for example, if you are testing for pregnancy, there are increased levels of certain hormones. In general you can tell things like if you have an infection, because of a high white blood cell count but then you will need more specific tests to tell you what kind of infection. I think for cancers its the same. Lukemia is in the blood so you could probably find that in a test, but other types you would have to have scans to find where exactly the cancer is. Ultimately, yes, things can be overlooked if doctors are looking for the wrong things.
5. Depending on the symptoms of the patient and what the Doctor suspects the patient has the Doctor selects certain tests to be done on a patient. This can be one test or a cobination. The blood is collected in vacutainer containers depending on which test needs to be done. These are tubes with different colored caps which contain certain substances in them depending on what needs to be tested. For example some allow coagulation while others don't. The tests which need to be done are passed through different parts of the laboratory for example hematology, clinical chemistry, immunology etc. The different tests which need to be done are done. For example for Leukemia the white cell count is determined while in pregnancy a blood count is done as well as blood typing and antibody screen. Brain cancer would probably most likely be detected by cat scans. things can be overlooked however blood tests do not diagnose they present results which if unusual are checked. They also give an interpretation of the results obtained. the ultimate diagnosis is made by the Doctor. Things can be overlooked as mistakes can be made, however there are many checks in place. If you are unsure you can go to another Doctor for a second opinion.
6. Most blood tests have only an indirect correlation with the disease that triggers the order. As a matter of fact, very few tests are specific for a particular disease. For instance, a person may have a mild anemia (low red blood cell count) because of pregnancy or because of cancer, or for any number of other reasons. The CBC drawn to check for anemia in either patient is the same test. There's no way to test for everything, and even if you have a test that's looking for a particular thing, there are always four possibilities: (1) the person has the disease, and the test says the person has the disease (2) the person has the disease, and the test says he doesn't (3) the person doesn't have the disease and the test says he does, or (4) the person doesn't have the disease, and the test says he doesn't. Not only are things overlooked, there are red herrings all over the place. Medicine is mostly about statistical probabilities. There's very little absolute truth.
7. NO... of course there are routine tests and specific tests, the routine ones usually direct towards a group of diseases, and then the specific ones are used to make definitive diagnoses. the probability of overlooking always remains, but can be minimized by a systematic approach.
8. When we order tests, we have to order specific tests - for example, a "serum HCG" (pregnancy test) or "complete blood count" (looking at numbers and types of different blood cells) The results of the tests are pieces of a puzzle that we use to make diagnoses or guide treatment. Sometimes the results of one test will suggest others that need to be done, or may confirm what we already suspect. Every now and then, something unexpected pops up, and that leads to further lines of exploration to find what is causing the abnormality. So, one blood test might show an abnormality that could turn out to be pregnancy or cancer, but that's not what the lab report will say. The report would say that the red cell count is low, or that platelets were high, or something similar. It is up to the doctor to put the pieces together and come up with the diagnosis. Can something be overlooked? Sure, it happens all the time. Add in the facts that sometimes lab values come back abnormal for no apparent reason, and that one abnormality may be present in dozens of diseases, and you start to get an idea why we spend so much time training.
9. Blood is the medium in which the whole body chemicals, nutrients, waste products, etc, carried from one place to the other within your body. It is cross section of your body function. It is like the high way network of the nation. If you sit near a high way and watch all the cars and trucks go by, you can get a good idea as to what is going on. 1. A school bus is going by, means that children are going to school. 2. Wal-Mart truck is going, means that merchandise are being delivered to the local store. 3. A fire truck is going, means there is a fire near by, etc. In a similar fashion, you can look for or find several chemicals, etc in your blood which are specific to diseases. For example, if your CPK-MB is positive, you had a heart attack during the last few hours, if your bilirubin is high you have liver disease, if you WBC is very high you have leukemia, if lead is high you have lead poisoning and so on.