By documenting a Streptococcal infection plus 2 major or 1 major and 2 minor criteria.
The major criteria are:
- Flitting polyarthritis
- Erythema marginatum
The minor criteria are:
- Arthralgia (joint pain only) without arthritis
- Blood tests indicating inflammation, i.e. raised erythrocyte sedimentation rate (ESR), raised C reactive protein (CRP) or a leucocytosis (raised white cell count)
- An abnormal electrocardiogram (ECG) especially a prolonged PR interval (do not use this minor criteria if carditis is used as a major criteria)
These are the modified Duckett-Jones criteria. A Streptcoccal infection is documented by a positive throat culture or a raised antistreptolysin O titre. A blood culture is useful to exclude bacterial endocarditis which should be considered in any child with fever and a murmur. Two minor criteria are needed to diagnose acute rheumatic fever in a child with establised rheumatic heart disease.
Always suspect acute rheumatic fever in an unwell child older than 3 years who presents with fever, tachycardia and shortness of breath or painful joints.
Strict clinical criteria are used to diagnose acute rheumatic fever.