Ruthie Landen, age 14, of Phoenix, Ariz., for her question:
HOW IS A DIAGNOSIS MADE?
Diagnosis is the art by which doctors determine which diseases are affecting their patients. Diagnosis is one of the most important branches of medicine. There are many different types of diagnosis. A clinical diagnosis is made completely from symptoms. A differential diagnosis is one that compares symptoms of several diseases to see which one is most likely to be causing the trouble. A biological diagnosis is made by performing tests on animals with a sample of one of the patients body fluids.
The X ray may be used to give a diagnosis of tuberculosis. A chemical analysis of the patients urine is often taken to see if the patient has diabetes.
One way of deciding what is wrong with a patient is to decide what disease he does not have. The doctor compares the sick person's symptoms with the known symptoms of various diseases. All the diseases are weeded out until it is fairly certain that the patient could have only one disease. This is called diagnosis by exclusion.
A laboratory diagnosis is made by studying the blood, urine or other liquids of the body in a laboratory, as in the case of anemia and diabetes.
A physical diagnosis is made by looking at the patient for signs of disease apparent to the eye, such as rashes or broken bones, and examining the patient with the hands.
A tentative diagnosis is sometimes made when the symptoms are not definite. The diagnosis is made, and the doctors give treatment for what they decide the disease to be, but they watch the patient closely for new symptoms.
When a patient is first seen, the doctor usually checks a few basic things immediately. He may look into the mouth to see if the patient's tongue is coated, or if his throat shows signs of an infection. He may also listen to the patient's heart and lungs with a stethoscope.
In the doctor's first examination, the simple diagnosis will also include a close look at the patient's eyes and ears. If the doctor hears something unusual in the heart action, he may make further heart diagnosis with an electrocardiograph machine. Terminals of wire conducting very small amounts of electricity are fastened to the patient's arms and legs so that they register the way the heart functions and record the movement on a graph. An irregular heart action will make an irregular line on the graph.
Modern methods of diagnosis have been aided by the invention of such devices as the electrocardiograph and the stethoscope, and by improvements in laboratory technique.
If cancer is suspected now, a small piece of tissue may be cut from the diseased part and examined in the laboratory to see if caoncerous cells are present. Smears of body fluids can be examined underneath the microscope as part of a diagnosis to identify the germ of a disease.