Chapter 27
Pharyngitis

Jesse M. Pines^1,2 and Christopher R. Carpenter³

¹ US Acute Care Solutions, Canton, OH, USA

² Department of Emergency Medicine, Drexel University, Philadelphia, PA, USA

³ Department of Emergency Medicine, Washington University School of Medicine, St. Louis, MO, USA

Highlights

Differentiating bacterial pharyngitis, specifically GAS (Group A Streptococci) infection from other causes of sore throat is a challenge.
The Centor criteria with the McIssac classification and the FeverPAIN criteria predict the probability of GAS infection based on clinical criteria.
While complications from GAS are relatively rare, in a large cohort study, many adult patients with low Centor and FeverPAIN scores had GAS‐related complications. This suggest that patients with intermediate scores on Centor and FeverPAIN may benefit from confirmatory rapid strep testing/cultures, or potentially delaying antibiotics before starting therapy to balance the avoid overtreatment of viral infections with the potential for GAS‐related complications.
There is an emerging discussion in the medical literature and guidelines as to whether antibiotics are beneficial in GAS because of the very high number needed to treat to prevent complications.

Background

The complaint of sore throat is common in emergency medicine, as well as in ambulatory settings such as doctor’s offices and clinics. In 2017, there were more than 1.186 million visits to US emergency departments (EDs) for acute pharyngitis, according to the National Hospital Ambulatory Medical Care Survey.¹ The most common bacterial cause for sore throat is Group A Streptococci (GAS). The value of using antibiotics has been debated for GAS because it usually resolves spontaneously without complications. However, antibiotics are currently recommended for patients in cases where there is a high likelihood of, or culture‐confirmed, streptococcal infection in the throat.²

Antibiotics for sore throat should prevent complications, reduce symptoms, and prevent transmission of the disease. A recent Cochrane review found that at 3 days, antibiotics reduced symptoms of sore throat, headache, and fever, as well as complications following GAS pharyngitis include suppurative (acute otitis media and acute sinusitis) and nonsuppurative complications (acute glomerulonephritis and acute rheumatic fever).³ Notably, the same Cochrane review highlights that most streptococcal pharyngitis studies occurred in the 1950s and with the shifting epidemiology of disease in high‐income countries (where absolute rates of complications are lower) the NNTB (number needed to treat for benefit) will rise above a rate at which it might be regarded as worthwhile to treat. In low‐income countries where the absolute rate may be much higher, the lower NNTB will mean antibiotics are more likely to be effective. A study in the UK reported that the overall incidence of suppurative complications in a large cohort to be low, on the order of 1.4% in an ambulatory population.⁴ In adults without a previous history of rheumatic heart disease the number needed to treat to prevent one case of rheumatic heart disease is 3 million.⁵ This literature suggests that the general paradigm for detecting and treatment GAS pharyngitis with antibiotics may need to be reconsidered.

Nonetheless, physicians routinely treat sore throat with antibiotics. Clinical gestalt is inadequate to rule in or rule out GAS pharyngitis, and no standardized diagnostic testing guideline exist for which ED patients with sore throat require antibiotics. Although rapid antigen detection and molecular tests exist, their cost‐effectiveness remains undefined.⁶ However, clinical decision rules such as the Centor criteria (Table 27.1) and FeverPAIN (Table 27.2) can help in risk‐stratifying patients who require testing. According to the American Academy of Family Practice, the statement, “Use of clinical decision rules for diagnosing GABHS pharyngitis improves quality of care while reducing unwarranted treatment and overall cost” was given an evidence grade A.⁹ The American College of Emergency Physicians and other groups within the specialty of emergency medicine have not released specific guidelines on pharyngitis.

Table 27.1 Centor score (modified McIssac) for strep pharyngitis

Source: Adapted from reference [7].

Patient age	3–14 yrs	+1
	15–44 yrs	0
	≥45 yrs	−1
Exudate or swelling on the tonsils	Yes	+1
	No	0
Tender/swollen anterior cervical lymph nodes	Yes	+1
	No	0
Temperature > 38 °C (100.4 °F)	Yes	+1
	No	0
Cough	Absent	+1
	Present	0
Centor score	Probability of GAS pharyngitis	Recommendation
0	1–2.5%	No further testing or antibiotics
1	5–10%	No further testing or antibiotics
2	11–17%	Optional rapid strep testing and/or culture
3	28–35%	Consider rapid strep testing and/or culture
≥4	51–53%	Consider rapid strep testing and/or culture. Empirical antibiotics may be appropriate

Clinical question

Which physical examination findings significantly alter the likelihood of a positive GAS culture in patients with sore throat?

A diagnostic systematic review compiled data and calculated likelihood ratios (likelihood ratio [LR]+ and LR−) for clinical findings and the chance of a positive GAS culture.¹⁰

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