A 7-year-old presents with fever, migratory polyarthritis, and a new soft heart murmur 3 weeks after a throat infection. ASO titer is 800 IU/mL (normal <200). Which Jones criterion is considered the MOST reliable indicator of carditis?

• A New apical systolic murmur (mitral regurgitation)
• B Prolonged PR interval on ECG (carditis)
• C Pathological regurgitation on echocardiography ✓
• D Pericardial rub

Explanation

The 2015 revised Jones criteria added subclinical carditis — pathological mitral or aortic regurgitation detected by echocardiography — as a major criterion for carditis, even in the absence of clinical murmur. This echocardiographic finding is the most sensitive and reliable indicator of carditis in rheumatic fever. A prolonged PR interval is a minor criterion; a clinical murmur alone without echo confirmation may be functional, reducing its specificity.

Reference: Ghai Essential Pediatrics, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.