Pharyngitis
Pharyngitis: Excerpt from The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
Frank S. Celestino
Nearly 5% of all primary care office visits are for “sore throat” (ST) or pharyngitis (1). Only a small minority (10% to 20%) of ST patients are infected with group A β-hemolytic streptococci (GABHS) (2–4). However, to minimize potential adverse effects of inappropriate antimicrobial therapy, it is important to accurately identify GABHS infection because it is the only commonly occurring form of pharyngitis for which antibiotic therapy is definitively indicated (3). Early identification and treatment of GABHS will help prevent rheumatic fever, provide symptom relief, reduce suppurative complications, and decrease infectivity.
Approach
A. Causes of ST. The differential diagnosis is extensive, but viruses and GABHS predominate in primary care as shown in the following list of likely causes of pharyngitis (2–5).
1. Viral: 50% to 80%
2. GABHS: 5% to 30% (mean 15%)
3. Epstein-Barr virus: 1% to 10%
4. Chlamydia pneumoniae: 2% to 5%
5. Mycoplasma pneumoniae: 2% to 5%
6. Neisseria gonorrhoeae: 1% to 2%
7. Other bacteria, fungi, parasites: all rare
8. Noninfectious causes (allergic rhinitis with postnasal drip, gastroesophageal reflux, foreign body, burns, neoplasms, radiation, inhaled or swallowed toxins, dryness, psychogenic, dust): all rare, except perhaps rhinitis and psychogenic
9. Referred pain (thyroiditis, dental): rare
B. Seasonality. Visits for ST occur year round but peak in winter. GABHS infection peaks in late winter and early spring (1).
C. Age distribution. Data show that the probability of GABHS pharyngitis in primary care by age is: 0 to 2 years (<1%), 2 to 4 (14%), 5 to 9 (34%), 10 to 19 (16%), adult (9%) (2). Infectious mononucleosis (IM) as a cause of ST peaks between ages 15 and 30 at a probability of 5% to 10%.
D. Chronicity. Most pharyngitis is acute and self-limited. When ST lasts longer than 2 to 3 weeks, consider noninfectious causes or atypical bacterial causes (e.g., chlamydia or mycoplasma) (4).
E. Special concerns include peritonsillar or retropharyngeal abscesses, epiglottitis, palatal cellulitis, toxic shock syndrome, Kawasaki’s disease, Stevens–Johnson syndrome, and Behçet’s syndrome.
History
Is there any history of seasonal allergies, trauma, malignancy, radiation therapy, inhalation, ingestion, thyroid dysfunction, or significant psychiatric illness? If so, then the possibility of a noninfectious cause of ST exists. How severe is the ST and how abrupt was the onset? Is there accompanying rhinitis, nasal congestion, cough, malaise, myalgias, rash, diarrhea, conjunctivitis, fever, tender or swollen “neck glands,” pain on swallowing, headache, nausea, vomiting, or abdominal pain? Classically, GABHS pharyngitis is severe and of acute ( <1 day) onset and accompanied by fever (temperature >101°F), painful swallowing, tender anterior cervical adenopathy and myalgias, but not cough or rhinitis. Headache, nausea, vomiting, and abdominal pain may be seen as well, especially in children. Conversely, the gradual onset of mild ST accompanied by rhinorrhea, cough, hoarseness, conjunctivitis, or diarrhea in an afebrile patient speaks strongly for a viral cause. Despite these broad generalizations, classic symptom complexes alone are neither sensitive nor specific enough to rely on for judging the need for antibacterial treatment (2–5). For example, the symptoms most likely to predict the presence of GABHS infection—fever and lack of cough—have sensitivities of 0.58 to 0.72 and specificities of only 0.43 to 0.67 (2). Additionally, the presence of a positive throat culture in the prior year or recent exposure to GABHS has high specificity, 0.90, but low sensitivity, 0.23 (2,3).
Physical examination
A. Focused physical examination (PE). This should include assessing vital signs (especially temperature) and examining the head, eyes, ears, nose, throat, neck, and skin. Findings classically associated with GABHS infection include palatal petechiae, intense (“beefy red”) tonsillopharyngeal erythema with exudates, tender anterior cervical adenopathy, and a scarlatiniform rash (Chapter 13.5). Conversely, absence of these features together with the presence of rhinitis, hoarseness, conjunctivitis, stomatitis, discrete ulcerative lesions, or a typical viral exanthem point toward a viral cause. In IM, the classic GABHS features are often combined with posterior cervical or generalized lymphadenopathy and hepatosplenomegaly. However, once again none of these physical findings in and of themselves have sufficiently high sensitivity and specificity to rely on for accurate diagnosis (2–4).
B. Additional PE. Abdominal examination is dictated by either gastrointestinal symptoms or the presence of severe fatigue with posterior cervical adenopathy (suggesting IM). Cough or fever should lead to pulmonary examination. Cardiac examination is important for toxic appearing patients.
Testing
A. Clinical laboratory tests. Because even experienced clinicians are unable to use the clinical presentation of pharyngitis to reliably predict the causative agent (because of inadequate sensitivity and specificity), accurate diagnosis should be based on results of a throat culture (TC) or rapid streptococcal antigen detection test (RSADT). In an untreated patient with streptococcal pharyngitis, a properly obtained (vigorously swabbing both tonsils and posterior pharynx) TC is almost always positive (sensitivity 90% to 95%) (3,4). Unfortunately, the culture does not reliably distinguish between acute GABHS infection and streptococcal carriers with concomitant viral infection. Streptococcal pharyngeal carriage, unfortunately, is a common finding particularly in school-aged children (20% to 30%) (2,3,5). A negative TC does permit the withholding of antimicrobial therapy (i.e., specificity = 0.99) (3–5).
Although methods vary, RSADTs do have high degrees of specificity (92% to 95%) (3,4). Unfortunately, their sensitivity in routine clinical practice is unacceptably low (60% to 85%) (3,4). Therefore, a negative antigen test does not exclude GABHS and a back-up throat culture must be obtained. Also, RSADTs suffer the same limitation as TCs because of the presence of carrier states.
Streptococcal antibody titers are of no immediate value in the diagnosis of acute GABHS pharyngitis.
If IM is suspected, a complete blood count and heterophil antibody testing can confirm the diagnosis reliably if the patient is in the second week of illness.
B. Imaging studies. None are usually necessary unless a serious suppurative sequela is suspected (e.g., retropharyngeal abscess).
Diagnostic assessment
Researchers have tried to incorporate clinical and epidemiologic features of acute pharyngitis into scoring systems that attempt to predict the probability of GABHS (2–5). Unfortunately, even the best of these predict positive TCs less than 70% of the time. Most scoring systems have incorporated the cardinal features such as fever, tender cervical adenopathy, tonsillar exudates, and lack of cough or rhinitis. Patients, especially adults, who have none of these features have a very low (<5%) probability of GABHS and no further testing is advised. For most other patients, who have varying numbers of cardinal features, the probability of GABHS is either intermediate (10% to 30%) or high (40% to 60%) and further testing is necessary, usually first with a RSADT and, if negative, a follow-up TC. Only in patients, usually children, with all the cardinal features plus a history of recent GABHS exposure or culture-proved recurrent streptococcal illness, can further testing be eliminated and empiric therapy begun.
References
1. National Ambulatory Medical Care Survey. Hyattsville, MD: National Center for Health Statistics, 1993.
2. Ebell MH. Sore throat. In: Sloane PD, Slatt LM, Curtis P, et al., eds. Essentials of family medicine, 3rd ed. Baltimore: Williams & Wilkins, 1998:632–634.
3. Bisno AL, Gerber MA, Gwaltney JM, Kaplan EL, Schwartz RH. Diagnosis and management of group A Streptococcal pharyngitis: a practice guideline—Infectious Disease Society of America. Clin Infect Dis 1997;25:574–583.
4. Komaroff AL. Sore throat and acute infectious mononucleosis in adult patients. In: Black ER, Bordley DR, Tape TG, et al., eds. Diagnostic strategies for common medical problems, 2nd ed. Philadelphia: American College of Physicians, 1999:229–242.
5. Perkins A. An approach to diagnosing the acute sore throat. Am Fam Physician 1997;55:131–138.>>>
Book Source Details
- Book Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
- Author(s): Robert B. Taylor (editor)
- Year of Publication: 2000
- Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2000 Lippincott Williams & Wilkins.
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