Viral

In addition to the characteristic pharyngeal pain and dysphagia, viral causes of pharyngitis may also produce low-grade fevers, cough, rhinorrhea, myalgias, or headaches. Viral causes may produce exudates as well, although cervical adenopathy is less common. Common viral causes include rhinoviruses, adenoviruses, Epstein-Barr virus (EBV), herpes simplex virus (HSV), and influenza and parainfluenza viruses. Less common viruses that may cause pharyngitis include respiratory syncytial virus, cytomegalovirus, and primary human immunodeficiency virus (HIV).

Pharyngitis in young adults may be due to infectious mononucleosis, an infection caused by EBV. It is often characterized by thick tonsillar exudates or membranes, as well as other systemic symptoms and signs. Splenomegaly (50%) is frequently present and generalized lymphadenopathy is usually present. Palatal petechiae and periorbital edema may likewise be seen.

Also a disease of young adults, HSV infection may produce a painful and characteristic pharyngitis. HSV pharyngitis is typically accompanied by painful vesicles on an erythematous base. These vesicles occur in the pharynx, lips, gums, or buccal mucosa. Fever, lymphadenopathy, and tonsillar exudates may also be present and last for 1 to 2 weeks. HSV pharyngitis may be either a primary infection or reactivation of a previous infection. In addition, bacterial superinfection of affected tissues may occur.

Bacterial

The most common cause of bacterial pharyngitis in children is GAβHS. It is less frequently implicated in patients older than 15 years. During epidemics, the incidence may double. Characteristic symptoms include tonsillar exudates, high fevers (temperature > 38.3° C), tender cervical adenopathy, and pharyngeal erythema. Headache, nausea, and abdominal pain may also be found. GAβHS pharyngitis usually lacks the traditional symptoms of viral infections (cough, rhinorrhea, myalgias). It occasionally produces a fine sandpaper-like rash that is termed scarlet fever.

Pharyngitis caused by Mycoplasma pneumoniae occurs in crowded conditions, may be associated with epidemics, and typically produces a mild pharyngitis. Symptoms include exudates and a hoarse voice, and it may also be associated with lower respiratory symptoms such as cough and occasionally dyspnea.

Chlamydia pneumoniae pharyngitis resembles Mycoplasma pharyngitis in its occurrence in epidemic and crowded conditions. This pharyngitis is classically described as severe and persistent with tenderness in the deep cervical lymph nodes and occasional associated sinusitis.

Gonococcal and Chlamydia trachomatis pharyngitis have varying manifestations from exudative to nonexudative, mildly symptomatic to severely symptomatic, and transient or persistent. These infections result from orogenital sexual transmission, and asymptomatic carriers exist and may unknowingly spread the disease.

F. necrophorum, known to be a factor in Lemierre syndrome, frequently causes pharyngitis in young adults and is a common causative agent of recurrent pharyngitis as well.

Viral

Diagnostic testing for viral pharyngitis is limited to only a few different specific causes. EBV infection may be diagnosed with a few different tests. The peripheral blood smears of up to 75% of patients with EBV demonstrate atypical mononuclear cells. An EBV monospot test may be positive in up to 95% of adults and 90% of children, but the test may not be positive during the first few days of illness. EBV IgM antibodies develop in 100% of patients but may also initially be negative.

Herpes pharyngitis is diagnosed by serologic tests, herpes culture, or cytopathologic tests from lesion scrapings. Primary HIV pharyngitis may be diagnosed with serologic tests such as Western blot and enzyme-linked immunosorbent assay. New rapid HIV tests using buccal swabs have also been shown to be effective in an ED setting.

Bacterial

Diagnostic testing for GAβHS is a subject of some controversy. Although the diagnosis of GAβHS infection is important in preventing many serious complications of streptococcal pharyngitis, including rheumatic fever, accurate diagnosis of GAβHS pharyngitis is notoriously difficult. The only valid method of diagnosing acute GAβHS infection involves acute and chronic antistreptolysin O titers. However, this method is far from practical in the emergency setting. Throat cultures have a sensitivity of nearly 90% for detecting Streptococcus pyogenes in the pharynx, but their accuracy may vary, depending on recent antibiotic use and culture and collection techniques.

Rapid diagnostic testing for GAβHS detects antigens via varying techniques, including latex agglutination, enzyme-linked or optical immunoassay, and DNA luminescent probes. Specificities are reported to be greater than 90% with sensitivities between 60% and 95%.³ A positive test appears to be a reliable indicator of the presence of GAβHS in the pharynx, but a number of factors must be considered. Some patients with a positive test may be asymptomatic carriers, and rapid tests may be negative in patients with low bacterial counts.

In addition to cultures and rapid streptococcal tests, a number of authors have proposed clinical criteria to aid in the diagnosis of GAβHS pharyngitis. The most well known are the Centor criteria and the McIssac modifications of these criteria. The modified Centor score gives one point each to temperature higher than 38° C, swollen tender anterior cervical nodes, tonsillar swelling or exudates, absence of upper respiratory tract symptoms (e.g., cough, coryza), and age between 3 and 15 years. If the patient is older than 45 years, a point is subtracted. If the score is 1 or less, no further testing or treatment is warranted. For scores of 2 to 3, further testing may be indicated, such as cultures or rapid streptococcal tests. For scores of 4 or higher, no further testing is required and all patients may receive antibiotics for GAβHS pharyngitis (Box 29.1).^4,5

In two recent guidelines (from the Infectious Diseases Society of America [IDSA] and the American Society of Internal Medicine [ASIM]), slightly different approaches to patients with pharyngitis have been proposed. In children the guidelines are similar and call for the use of a rapid test in all children; those with a positive test are treated, those with a negative test undergo a throat culture, and those with a positive culture result are treated. The guidelines have suggested different approaches to adults with pharyngitis, however. The IDSA guidelines propose treating all adults in a fashion similar to their pediatric recommendations.⁶ The ASIM guidelines, though, allow two additional approaches for adults, including performing a rapid test on all adults with a Centor score of 2 or 3 and treating those with a positive test result, as well as empirically treating all patients with a score of 4 or higher. The final approach endorsed by the ASIM suggests testing no adults but treating all adults with a Centor score of 3 or 4 empirically.⁷ A recent analysis comparing the different recommendations found that an approach using throat cultures had a sensitivity of 100%; approaches using rapid treptococcal tests involving clinical criteria alone had sensitivities of approximately 75%. Furthermore, the specificity of clinical criteria alone was below 50%, thus suggesting that many adults were prescribed antibiotics for pharyngitis unnecessarily.⁸

Diagnostic testing for other causes of bacterial pharyngitis requires either culture on special media (Thayer-Martin agar for gonococcal infection) or specialized antigen or serologic testing. Mycoplasma infection may be detected by culture, serologic testing, or rapid antigen testing. Antigen detection may also be used for chlamydial infection, as well as culture or serologic testing.