Each diagnostic technique has its own characteristics and gives different information about the condition and functioning of a given organ. Generally there are research protocols that any doctor will follow, and these establish an order of which tests to carry out in seeking the cause of a problem. A simple X-ray can be enough to tell if a patient has arthrosis, for example, without having to subject him or her to more complicated and costly procedures.

The most common diagnostic tests are blood analysis and X-rays. A small sample of blood can reveal anaemia and give data on the body's defenses - this shows the existence of infections - levels of cholesterol and risk of suffering cardiovascular problems. It also gives data on blood sugar and the functioning of the liver, among other things. Ultimately it is a simple procedure that gives a broad view of the patient's general state of health.

For their part, X-rays use electromagnetic energy to create images of the body's more dense tissues. This can reveal problems with bones or the presence of a tumor. They are reliable for detecting multiple bone alterations and diagnosing lung diseases ranging from edemas to tuberculosis, and also problems with the blood vessels of the heart. A variant of the traditional X-ray is the mammogram, an essential tool for detecting breast tumors.

Another common diagnostic tool is the electrocardiogram. It gives a graphic representation of the electrical impulses generated by the heart, and is applied by placing electrodes at different spots around the body. It requires no special preparation of the patient and gives reliable data on arrhythmia, alterations in the chambers of the heart or the pericardium, as well as on the body's ions: potassium, sodium and calcium. Electrocardiograms also help gauge a person's risk of suffering a heart attack.

Another instrument based on the same technique is the encephalogram. It observes the electrical activity of the brain, and this gives information on the presence of encephalitis, epilepsy and toxic or metabolic encephalopathies. It is also used to monitor patients in coma.

One test that has become widespread is the sonogram. It involves the emission of ultrasound that is converted into images by a computer. The test is innocuous for the patient and not terribly costly, and is used to observe the condition of a variety of organs. Sonograms are common during pregnancy and very useful for checking the condition of the fetus. But there are also Doppler sonograms that let doctors see the functioning of the body's structures and evaluate blood flow. Abdominal, renal and mammary sonograms round out information given by mammograms and sono-cardiograms which give data on the heart's functioning and pumping, and vascular sonograms.

CAT Scans - computerized axial tomographies - are a tool that feature an X-ray tube similar to those of normal X-rays. But the image is picked up by�highly sensitive sensors and later computerized. The image is treated with digital data, which allows a detailed study of the areas being studied. It allows cross-sectional images of organs. The test can be done with contrast or without. It is normally used to diagnose ailments in the head and neck, from traumatism to cerebro-vascular accidents to tumors, thorax problems and woes of the liver, pancreas and kidney.

Magnetic resonance is another technique that involves images. It does not use X-rays, and its functioning - based on hydrogen molecules and electromagnetic fields - is quite complex. The test lasts from 10 to 50 minutes and is used to complete a CAT Scan study. It is very useful in studying degenerative diseases of the nervous system and joints - above all the meniscus and ligaments.

Finally, there is the biopsy. This method is highly reliable but uncomfortable for the patient because it is an invasive procedure. A small sample of tissue is extracted. Such tests are essential to determine if a tumor is benign or malignant, or to determine the characteristics and composition of other abnormal growths in the body.