For a patient with recurrent sore throat, is a rapid antigen detection test (RADT) or throat culture required before prescribing antibiotics?

Is Throat Culture or RADT Required for Recurrent Sore Throat?

Yes, microbiologic confirmation with either RADT or throat culture is mandatory before prescribing antibiotics for recurrent sore throat—clinical assessment alone is insufficient, and the specific testing strategy depends on patient age. 1

Age-Based Testing Algorithm

Children and Adolescents (Ages 3-15)

• Perform RADT first as the initial diagnostic test when clinical features suggest possible streptococcal infection (sudden-onset sore throat, fever, tonsillar exudate, tender anterior cervical lymphadenopathy, absence of cough). 1, 2
• A negative RADT must be followed by throat culture because RADT sensitivity in children is only 80-90%, missing 10-20% of true Group A streptococcal infections. 3, 1
• This two-step approach is required due to the higher prevalence of Group A streptococcus (20-30%) and greater risk of acute rheumatic fever in this age group. 1
• Treatment can be initiated within 9 days of symptom onset and still prevent acute rheumatic fever, so waiting for culture results does not compromise outcomes. 1

Adults

• A negative RADT alone is sufficient to rule out Group A streptococcal pharyngitis—no backup throat culture is needed. 3, 1
• This single-step approach is justified because adults have only 5-10% prevalence of Group A streptococcus and extremely low risk of acute rheumatic fever. 1
• The specificity of RADT is ≥95%, making false-positive results rare and allowing confident treatment decisions based on positive results. 3, 1

Children Under Age 3

• Do not test or treat for Group A streptococcal pharyngitis in this age group, as the infection and acute rheumatic fever are rare. 1
• The exception is when an older sibling has confirmed Group A streptococcal infection. 1

When NOT to Test

Skip testing entirely when viral features are present, as these strongly indicate viral etiology and testing will likely identify harmless carriers rather than true infection: 1

• Cough (most important viral indicator) 1, 2
• Rhinorrhea/nasal congestion 1
• Hoarseness 1
• Conjunctivitis 1
• Oral ulcers 1

Management Based on Test Results

Positive RADT or Culture

• Prescribe penicillin V or amoxicillin for 10 days as first-line therapy. 3, 1
• Penicillin V dosing: 250 mg 2-3 times daily for children <27 kg; 500 mg 2-3 times daily for children ≥27 kg and adults. 1
• Amoxicillin dosing: 50 mg/kg once daily (maximum 1 g) for 10 days. 1
• For penicillin-allergic patients without anaphylaxis: first-generation cephalosporin for 10 days. 1
• For anaphylactic penicillin allergy: clindamycin 20 mg/kg/day divided three times daily (maximum 1.8 g/day) or azithromycin 12 mg/kg once daily (maximum 500 mg) for 5 days. 1

Negative Test Results

• Withhold antibiotics entirely and provide only symptomatic treatment (acetaminophen or ibuprofen for pain and fever). 1
• The vast majority of test-negative cases are viral and self-limited. 1
• Up to 70% of patients with sore throat receive unnecessary antibiotics, while only 20-30% actually have Group A streptococcal pharyngitis. 1

Critical Pitfalls to Avoid

• Never prescribe antibiotics based on clinical appearance alone, even with tonsillar exudate or white patches—these findings overlap extensively between viral and bacterial causes. 1
• Do not test or treat asymptomatic household contacts, even with recurrent infections—up to one-third may be asymptomatic carriers, and prophylactic treatment does not reduce subsequent infection rates. 1
• Do not perform routine follow-up testing after completing appropriate antibiotic therapy in asymptomatic patients—positive post-treatment tests often reflect carrier status rather than treatment failure. 1
• In recurrent pharyngitis, consider chronic carrier state with superimposed viral infections rather than assuming repeated true streptococcal infections. 1

Special Considerations for Recurrent Episodes

• For multiple recurrences after appropriate treatment, consider alternative regimens such as clindamycin, amoxicillin-clavulanate, or a first-generation cephalosporin rather than repeating penicillin. 4
• Distinguish true reinfection from carrier state by evaluating for viral symptoms (cough, congestion, rhinorrhea) that suggest intercurrent viral infection in a streptococcal carrier. 4
• Consider testing household members only if there are multiple repeated episodes suggesting "ping-pong" transmission within the family. 4