Sore throat is a common complaint in the emergency department and outpatient clinic setting. “Strep throat” caused by Streptococcus pyogenes accounts for just 5%-15% of all adult pharyngitis and tonsillitis. Most cases are caused by viruses, yet more than 75% of adult patients receive antibiotics. Why do we prescribe antibiotics? The answers are many:¹

• It is clinically difficult to determine who actually has pharyngitis caused by S. pyogenes.
• Testing takes time and is expensive.
• If only culture is available, there can be no point-of-service answer.
• Explaining to uninformed patients why antibiotics are indicated only in certain situations is time-consuming and can be frustrating.
• Medical-legal concerns (rheumatic fever and suppurative complications, such as peritonsillar abscess) may be a factor.
• Patients expect and “demand” antibiotics (customer satisfaction concerns).

Overall, it may be easier to just write the prescription! Let’s pose some simple questions about “sore throats” and get some (hopefully) simple answers on effective diagnosis and management.

Which Patients Get “Strep Throat”?

Most cases (40%-60%) of pharyngitis are caused by viral infections, with the remainder caused by other bacterial infections, fungal infections, or irritants (pollutants or chemicals).² Group A beta-hemolytic streptococcus (GABHS) pharyngitis is more common in children and adolescents between 5 and 15 years old, especially during the late autumn, winter, and early spring months in temperate climates (20%-30%). Adults have a much lower prevalence of GABHS infection (5%-15%).

The most common bacterial etiology of pharyngitis is GABHS. Other less-frequent isolates include group C and G strep, Fusobacterium necrophorum,³ Neisseria gonorrhoea, Corynebacterium diphtheriae (diphtheria), Mycoplasma pneumoniae, and several chlamydial species.^4,5

Viral vs. Strep Pharyngitis

Can we reliably distinguish viral from GABHS pharyngitis by history and physical alone? The short (and perhaps unpopular) answer is no. Experienced physicians are about 50%-60% accurate in their clinical ability to diagnose GABHS pharyngitis. However, we can use some data to help raise or lower our suspicion for GABHS. Figure 1 shows the clinical and epidemiologic findings associated with GABHS and viral pharyngitis.⁶

The most widely accepted prediction rule to help clinically distinguish the presence of GABHS pharyngitis is the Centor criteria. For the Centor score, 1 point is assigned for each of these clinical characteristics: history of fever, anterior cervical lymphadenopathy, exudates on the tonsils, and absence of a cough.⁷