Making the Diagnosis
The actual quantity of bacteria in the systems of people with rheumatic fever is often so low that the bacteria are undetectable. Doctors rely on a standardized checklist to identify the disease.
If you have a recent history of streptococcal infection, and at least 2 symptoms from a list of 5 common symptoms: arthritis, chorea, erythema marginatum, nodules under the skin, and carditis, your doctor may diagnose you with rheumatic fever.
Your doctor will listen to your heart with a stethoscope to help detect carditis. The diagnosis can also be made with only one of these common symptoms if other abnormalities are present at the same time. These include: sore joints, fever, rheumatic fever in the past, a specific abnormality on electrocardiogram (ECG; prolonged PR interval), or specific abnormalities on blood testing (elevated C-reactive protein or sedimentation rate).
Certain tests can also support the diagnosis by detecting antibodies the body produce against the Streptococcus bacteria, or by detecting the bacteria itself.
Before making any treatment decisions, your doctor will want to rule out other conditions that can affect the heart. Tests like the echocardiogram (ultrasound of the heart) can reveal the presence of congenital heart defects that might be confused with rheumatic fever.