Rheumatic Fever - Diagnosis
Diagnosis of rheumatic fever can be difficult because patients may have one, two, or more of the five symptoms listed above. The five symptoms for which a doctor looks include arthritis, chorea, carditis, erythema marginatum, and subcutaneous nodules. Fever is also present. However, fever by itself is not of much use in making a diagnosis. Many kinds of medical disorders have fever as a symptom.
Gerhard Domagk was a German biochemist who was born on October 30, 1895. He earned his medical degree in 1921 and then took a job with a large company, Farbenindustrie. Farbenindustrie manufactured industrial dyes.
Domagk was interested in finding out whether any of the dyes produced by Farbenindustrie had biological effects on animals. In one study, he injected a dye called Prontosil Red into a group of experimental mice. The mice had been given a streptococcus infection. Domagk was amazed to discover that the mice were cured of their disease by the dye.
That discovery might have lead nowhere except for a terrible event in Domagk's life. His daughter Hildegarde pricked herself with a knitting needle and developed a streptococcal infection herself. In desperation, Domagk injected Prontosil Red into his daughter. Again, the dye seemed to work miracles. Hildegarde quickly recovered from the disease.
Shortly after these events, the French chemist Daniele Bovet explained how Prontosil Red works. He showed that only one part of the compound was involved in killing bacteria. That part was a molecule called sulfanilamide. Sulfanilamide was the first of a large group of related compounds, called sulfanamides (or "sulfa drugs") to be used against bacterial infections.
A number of laboratory tests are also used to diagnose RF. For example, a throat smear can be taken to look for the presence of streptococcal bacteria. In a throat smear, a cotton swab is rubbed across the back of the patient's
throat. The material collected on the swab is then placed in a warm, moist environment for twenty-four to seventy-two hours. Any bacteria present in the material begin to grow during that period. If streptococcal bacteria are present, they can be seen with a microscope.
Laboratory tests can also be used to look for antibodies to the streptococcal bacteria. Blood taken from the patient's arm can be treated with chemicals that make these antibodies show up. The presence of the antibodies means that the patient has been infected with the streptococcal bacteria.
An electrocardiogram (ECG; pronounced ih-LEK-tro-KAR-dee-o-gram) can also be used to diagnose RF. An electrocardiogram is a test that measures the electrical activity of the heart. If the heart has been damaged by carditis, its electrical rhythms will be different from those of a healthy heart.
All of these symptoms and tests taken together can provide a diagnosis of rheumatic fever.
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