As rheumatic fever can cause so many different symptoms, a 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 usually 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's chorea)
- a painless, non-itchy skin rash (erythema marginatum)
- bumps or lumps that develop underneath the skin (subcutaneous nodules)
The minor signs and symptoms are:
- joint pain, but less severe than arthritic joint pain
- a high temperature (fever), usually over 39C (102F)
- blood tests that 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, or there are two minor, and one or more other major, signs or symptoms.
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.
You'll usually need to have an electrocardiogram (ECG). During an ECG, a number of small, sticky sensors called electrodes are attached to your arms, legs and chest. These are connected by wires to an ECG machine.
The ECG machine measures your heart's electrical activity, allowing your doctor to check for any abnormal heart rhythms. Heart inflammation is a common complication of rheumatic fever. It's important that any abnormal heart rhythms are detected early so that prompt treatment can be given.
A number of different blood tests may also be used to look for indications of rheumatic fever. These include:
- C reactive protein (CRP) – which tests the level of C reactive protein (CRP) in your blood. CRP is produced by the liver. If there's more CRP in the blood than usual, there's 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, the red blood cells will settle higher up the tube. If these substances aren't present, the blood cells will be lower down the tube.