What is the recommended treatment for a patient with elevated Anti-Streptolysin O (ASO) titre and Rheumatoid Factor (RF), indicating a streptococcal infection and autoimmune component?

Treatment for Elevated ASO Titre (271) and Rheumatoid Factor (66)

Critical First Step: Determine Clinical Context

Your immediate priority is to eradicate any residual Group A Streptococcus infection with a full 10-day course of penicillin, regardless of current throat culture results, as this prevents progression to rheumatic fever and permanent cardiac damage. 1, 2

The elevated ASO titre (271) indicates recent streptococcal infection, while the rheumatoid factor (66) requires careful interpretation—RF can be transiently elevated in post-streptococcal conditions and does not automatically indicate rheumatoid arthritis. 3

Primary Antibiotic Treatment

First-Line Options (Choose One):

• Oral Penicillin V: 500 mg twice or three times daily for 10 days for adults/adolescents, or 250 mg twice daily for children <27 kg 4, 1, 2

• Oral Amoxicillin: 50 mg/kg once daily (maximum 500 mg) for 10 days—this offers better compliance due to once-daily dosing 2, 5

• Intramuscular Benzathine Penicillin G: Single injection of 1,200,000 units for patients ≥27 kg or 600,000 units for patients <27 kg—strongly preferred if compliance is questionable or if there is personal/family history of rheumatic fever 1, 6

For Penicillin Allergy:

• Azithromycin 500 mg once daily for 5 days, or clarithromycin 250 mg twice daily for 10 days 6
• First-generation cephalosporins if no immediate-type hypersensitivity 4, 6

Critical caveat: The 10-day duration is mandatory—shorter courses significantly increase rheumatic fever risk. 2, 5 Treatment can be initiated up to 9 days after symptom onset and still prevent rheumatic fever. 4

Essential Clinical Assessment Required

You must evaluate for signs of acute rheumatic fever or other post-streptococcal complications:

• Cardiac involvement: New murmur, pericardial friction rub, cardiomegaly, heart failure signs 2, 6
• Joint manifestations: Migratory polyarthritis affecting large joints 2
• Neurological: Chorea (involuntary movements) 2
• Dermatological: Erythema marginatum, subcutaneous nodules 2
• Renal: Hematuria, proteinuria, edema, hypertension (post-streptococcal glomerulonephritis) 2

Regarding the Rheumatoid Factor Elevation

Do not assume rheumatoid arthritis based solely on RF=66 in the context of elevated ASO. 3

• RF can be transiently elevated in post-streptococcal reactive arthritis and other acute infections 3
• Classic rheumatic fever is now rare in adults, but reactive arthritis triggered by streptococci is well-documented 3
• If joint symptoms are present, they may represent post-streptococcal reactive arthritis rather than RA 3

If Acute Rheumatic Fever is Diagnosed

Immediate Actions:

1. Complete the 10-day penicillin course even if throat culture is negative 1, 6

2. Initiate continuous secondary prophylaxis immediately with benzathine penicillin G 1,200,000 units IM every 4 weeks (every 3 weeks in high-risk situations) 1, 6

3. Anti-inflammatory therapy:

   • High-dose aspirin 75-100 mg/kg/day for arthritis and mild carditis, continued for 4-6 weeks 1
   • Corticosteroids (prednisone 1-2 mg/kg/day) for severe carditis or inflammation 6

Duration of Secondary Prophylaxis (Critical—Do Not Stop Prematurely):

• With persistent valvular disease: At least 10 years or until age 40 (whichever is longer), often lifelong 1, 6
• With carditis but no residual valve disease: 10 years or until age 21 (whichever is longer) 6
• Without carditis: 5 years or until age 21 (whichever is longer) 6

Follow-Up Protocol

• Repeat clinical assessment at 3-5 days after starting therapy, then weekly until asymptomatic 2
• Monitor for development of carditis or glomerulonephritis for several months 2
• Patient becomes non-contagious after 24 hours of antibiotic therapy 4, 1

Common Pitfalls to Avoid

• Never use broad-spectrum antibiotics (e.g., third-generation cephalosporins) when narrow-spectrum penicillin is appropriate—this increases cost and antibiotic resistance 1
• Do not rely on a single ASO measurement—titers remain elevated for months after uncomplicated infections 4, 7
• Do not stop prophylaxis prematurely if rheumatic fever is diagnosed—at least one-third of cases result from asymptomatic infections, making recurrence prevention critical 6
• Remember that ASO testing has no role in diagnosing acute pharyngitis—it only confirms previous streptococcal infection 2