eMedicine Specialties > Infectious Diseases > HEENT Infections

Pharyngitis, Viral: Differential Diagnoses & Workup

Author: KoKo Aung, MD, MPH, FACP, Associate Professor, Department of Medicine, University of Texas Health Science Center; Adjunct Assistant Professor of Public Health, University of Texas School of Public Health
Coauthor(s): Ambrish Ojha, MD, Staff Physician, Department of Internal Medicine, Texas Tech University Health Sciences Center; Carson Lo, MD, Staff Physician, Department of Medicine, Memorial Hermann Southwest Hospital
Contributor Information and Disclosures

Updated: Jan 20, 2009

Differential Diagnoses

Other Problems to Be Considered

Streptococcal pharyngitis
Gonococcal pharyngitis
Other bacterial pharyngitis
Peritonsillar abscess
Diphtheria
Pharyngeal candidiasis
Noninfectious pharyngitis (eg, allergies; environmental factors; psychosomatic sore throat; sore throat caused by excessive shouting, cheering, or singing; dryness of the throat caused by nasal blockade, obstructive sleep apnea, palatal dysfunction, or mouth breathing)

Workup

Laboratory Studies

  • The similarity of signs and symptoms of viral pharyngitis make a specific etiological diagnosis virtually impossible without various laboratory tests. In many circumstances, etiological diagnosis is of no practical use because it may not alter the treatment and prognosis. Viral cultures are not needed to diagnose pharyngitis other than in a research setting.
  • The total WBC count may initially be slightly elevated without bandemia, followed by a decrease to fewer than 5000 cells/µL after 4-7 days of illness in about 50% of cases.
  • Atypical lymphocytosis is frequently associated with EBV and CMV infections.
  • Results from a rapid streptococcal antigen test and a bacterial culture of throat swab in viral pharyngitis may be positive (approximately 30% of patients with EBV infectious mononucleosis are colonized with group A streptococci).
  • Common cold: Specific virological diagnosis is unnecessary for practical purposes because it may not alter the management. Cultures of nasal secretions, serological tests, and polymerase chain reaction (PCR) techniques can be used for specific virological diagnosis. Rapid viral antigen detection tests are not sensitive enough to be useful.
  • EBV infectious mononucleosis: After week one of illness, peripheral blood film reveals relative and absolute lymphocytosis, with more than 10% atypical lymphocytes. Hemolytic anemia and thrombocytopenia secondary to anti-i antibodies are occasionally observed. Erythrocyte sedimentation rate (ESR) is elevated and liver function test results are mildly abnormal in about 90% of cases. Heterophile agglutination test (immunoglobulin M [IgM] antibody) results are positive with a titer of 40-fold or greater in 90% of affected adolescents and adults within the first few weeks after the onset of infectious mononucleosis symptoms. A mononucleosis spot test (Monospot) allows rapid screening for heterophile antibodies. Heterophile test results are usually negative in children younger than 4 years. Positive results for IgM antibody to viral capsid antigen and positive results for antibody to early antigen are useful to diagnose acute infection, particularly in cases that are heterophile negative.
  • Influenza: Leukopenia and proteinuria are nonspecific findings in influenza. Virus isolation or detection of viral antigen in respiratory secretions is very useful to diagnose acute illness. Virus can be readily isolated from nasal swab specimens, throat swab specimens, nasal washes, or combined nose-and-throat swab specimens by inoculation of embryonated eggs or cell cultures. Rapid detection of viral antigen directly in respiratory secretions can be accomplished by immunofluorescent (IF) studies, time-resolved immunofluorescence assay (TRFIA), radioenzyme immunoassay, and enzyme-linked immunosorbent assay (ELISA).
  • PCR techniques have been described for rapid detection of influenza virus RNA in clinical samples. Serological tests can be used, but they are not helpful for diagnosis and treatment of acute disease secondary to delay in obtaining the antibody titers in convalescent sera. Serological tests are useful for epidemiological purposes. A rise in complement-fixing and hemagglutination-inhibiting antibody levels during the second week is considered diagnostic of acute infection.
  • Enterovirus infection: Positive results on an enteroviral-specific reverse transcriptase-polymerase chain reaction (RT-PCR) test of throat swabs are diagnostic. Etiological diagnosis is not necessary for clinical purposes because it may not alter treatment.
  • RSV infection: RSV antigen in nasal secretions can be reliably detected with commercially available rapid tests.
  • CMV infection: A relative lymphocytosis is characteristic of acute CMV pharyngitis. Atypical lymphocytes may represent 10% or more of the total. CMV can be readily isolated from a throat swab. Positive results on the CMV-specific IgM antibody titers are diagnostic of acute infection. Results of heterophile tests are usually negative (heterophile-negative mononucleosis syndrome). A 4-fold or greater rise in antibody titers is confirmatory but useful only for epidemiological purposes.
  • Acute retroviral syndrome (primary HIV infection): Serological test results for HIV are usually negative during the phase of acute retroviral syndrome because the test takes approximately 4 weeks for seroconversion. HIV RNA assay by PCR technique and p24 antigen assay can be used to help confirm the diagnosis. HIV viral load is usually extremely high. The peripheral blood picture may resemble infectious mononucleosis. Heterophile test results are usually negative (heterophile-negative mononucleosis syndrome).

More on Pharyngitis, Viral

Overview: Pharyngitis, Viral
Differential Diagnoses & Workup: Pharyngitis, Viral
Treatment & Medication: Pharyngitis, Viral
Follow-up: Pharyngitis, Viral
References
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References

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Further Reading

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Keywords

viral pharyngitis, sore throat, acute pharyngitis, rhinoviral pharyngitis, adenoviral pharyngitis, EBV pharyngitis, HSV pharyngitis, influenzal pharyngitis, parainfluenzal pharyngitis, coronaviral pharyngitis, enteroviral pharyngitis, echoviral pharyngitis, RSV pharyngitis, CMV pharyngitis, cytomegaloviral pharyngitis, common cold, flu, influenza, pharynx, tonsils, upper respiratory tract infection, URTI, rhinovirus, adenovirus, Epstein-Barr virus, EBV, herpes simplex virus, HSV, parainfluenza virus, coronavirus, enterovirus, respiratory syncytial virus, RSV, cytomegalovirus, CMV, human immunodeficiency virus, HIV, coxsackievirus, echovirus, acute retroviral syndrome, infectious mononucleosis, IM, group A beta hemolytic streptococcus, GABHS

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Contributor Information and Disclosures

Author

KoKo Aung, MD, MPH, FACP, Associate Professor, Department of Medicine, University of Texas Health Science Center; Adjunct Assistant Professor of Public Health, University of Texas School of Public Health
KoKo Aung, MD, MPH, FACP is a member of the following medical societies: American College of Physicians
Disclosure: Nothing to disclose.

Coauthor(s)

Ambrish Ojha, MD, Staff Physician, Department of Internal Medicine, Texas Tech University Health Sciences Center
Ambrish Ojha, MD is a member of the following medical societies: American College of Physicians and American Medical Association
Disclosure: Nothing to disclose.

Carson Lo, MD, Staff Physician, Department of Medicine, Memorial Hermann Southwest Hospital
Carson Lo, MD is a member of the following medical societies: American College of Physicians-American Society of Internal Medicine, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, and Texas Medical Association
Disclosure: Nothing to disclose.

Medical Editor

Gregory William Rutecki, MD, Associate Professor, Program Director, Department of Internal Medicine, Feinberg School of Medicine, Northwestern University
Gregory William Rutecki, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Society of Nephrology, National Kidney Foundation, and Society of General Internal Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Gordon L Woods, MD, Consulting Staff, Department of Internal Medicine, University Medical Center
Gordon L Woods, MD is a member of the following medical societies: Society of General Internal Medicine
Disclosure: Nothing to disclose.

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

 
 
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