There are no specific tests to diagnose rheumatic fever. Instead, physicians rely on observing any symptoms that may appear following an infection with streptococcus bacteria. Over time, a model has been developed to help guide physicians to diagnose rheumatic fever. A diagnosis can be made if a patient has two major manifestations, or one major and two minor manifestations.

The major manifestations include:

• Arthritis in the joints.
  
  
• Chorea. This describes inflammation of the central nervous system, resulting in involuntary dance-like movements.
  
  
• Rash.
  
  
• Lumps under the skin (subcutaneous nodules).

The minor manifestations include:

• Fever
• Joint pain
• Previous rheumatic fever or rheumatic heart disease

There is some evidence that a test for C-reactive protein (CRP) may also help physicians diagnose rheumatic fever. Because rheumatic fever is an inflammatory disease, blood levels of C-reactive protein are abnormal during the rheumatic process.