Investigations monitor inflammation, seek evidence of preceding streptococcal infection and assess cardiac involvement.
Monitoring inflammation
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Measure erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), which are useful for monitoring disease progress.
Evidence of streptococcal infection
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Throat cultures should be taken, but only 10%–25% are positive because the infection has often resolved by presentation.
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Antistreptolysin O antibody (ASO) serology should be performed and provides supportive diagnostic evidence.
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ASO results are normal in one-fifth of adult cases of acute rheumatic fever and in most cases of chorea.
Cardiac assessment
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Echocardiography should be performed. It typically shows mitral regurgitation with mitral annular dilatation and prolapse of the anterior mitral leaflet.
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Echocardiography may also demonstrate aortic regurgitation and pericardial effusion.
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Cardiac biomarkers, including troponin and BNP, can be elevated.