As rheumatic fever can cause so many different symptoms, a type of checklist known as the "Jones Criteria" is used to help diagnose it.

Your GP will use the Jones Criteria to check for the signs and symptoms strongly associated with rheumatic fever.

These are divided into:

• major signs and symptoms – which you would normally expect to see in a case of rheumatic fever
• minor signs and symptoms – which can sometimes occur in a case of rheumatic fever

The major signs and symptoms are:

• inflammation of the heart (carditis) – which can cause symptoms such as shortness of breath and chest pain
• pain and swelling (arthritis) affecting multiple joints
• jerky involuntary body movements and emotional outbursts (Sydenham chorea)
• a painless, non-itchy skin rash (erythema marginatum)
• bumps or lumps developing underneath the skin (subcutaneous nodules)

The minor signs and symptoms are:

• joint pain, but less severe than arthritis joint pain
• a high temperature (fever), usually over 39ºC (102ºF)
• blood tests show you have high levels of inflammation in your body
• an irregular heart rhythm

A confident diagnosis of rheumatic fever can usually be made if:

• at least two major signs and symptoms are present
• there are two minor, and one or more other major, signs or symptoms

Testing

While some of the signs and symptoms listed above can be assessed by a physical examination, others – such as inflammation of the heart – need to be tested. Tests used to diagnose rheumatic fever are outlined below.

Electrocardiogram (ECG)

You will usually need to have an electrocardiogram (ECG). During an ECG, up to 12 sticky pads containing electrodes are attached to certain areas of the body, such as the arms, legs and chest. This procedure is painless.

A machine then measures the electrical activity of your heart, so that your doctor can check for any abnormal heart rhythms. Inflammation of the heart is a common complication of rheumatic fever. It is important that any abnormal heart rhythms are detected early on so that prompt treatment can be given.

Blood tests

A number of different blood tests may also be used to look for indications of rheumatic fever.

• C reactive protein (CRP) – this tests the level of C reactive protein (CRP) in your blood. CRP is produced by the liver. If there is more CRP in the blood than usual, there is inflammation in the body.
• Antistreptolysin O titre (ASOT) – this blood test looks for evidence of antibodies produced by the immune system in response to the streptococcal infection.
• Erythrocyte sedimentation rate (ESR) – in an ESR test, a sample of your red blood cells is placed into a test tube of liquid. If the blood is "sticky" due to various substances produced during the immune response, then the red blood cells will settle higher up the tube when it stands up. If these substances are not present, the ESR will be lower.