Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (603 page)

   For adults, the Centor criteria for adults are listed below. The probability of GAS infection increases with the number of criteria present: the presence of three or four is reported to have a positive predictive value up to 60%; the presence of 0 or 1 is reported to have a negative predictive value of 80%.

   Tonsillar exudates

   Tender anterior cervical adenopathy

   Fever or fever history

   Absence of cough

   Diagnosis

   Culture: Throat culture is the “gold standard” for the diagnosis of pharyngitis due to GAS, with sensitivity in the 90–95% range. The specificity is very high in patients with acute pharyngitis, but “false-positive” cultures, in terms of active disease, may be seen in chronic GAS carriers or after recent, successful therapy. Cultures for “test of cure” are not recommended, except for patients at very high risk for acute rheumatic fever.

   Direct antigen detection: Direct antigen tests are also available for rapid detection of GAS; however, these assays are not as sensitive as throat cultures. The sensitivity of antigen tests varies by technique and specific kit used, ranging from 60–95%; the specificity of most tests exceed 95%. Therefore, throat culture should be performed to confirm negative antigen tests but are not needed to confirm positive tests.

   
Molecular tests
: An FDA-approved molecular diagnostic assay is available for the detection of
S. pyogenes
in pharyngeal specimens. Sensitivity of the assay is 88–95% with specificity of 98–99.7%. The high sensitivity and specificity for this test allow test results to stand without the need for confirmation of positive or negative tests.

ACUTE RHINOSINUSITIS

   Definitions

Acute rhinosinusitis (ARS) is an inflammatory condition of the nasal and sinus mucosal tissues that resolves in fewer than 4 weeks, usually within 10 days. ARS is most commonly caused by respiratory viruses (like rhinovirus, parainfluenza virus, and influenza virus); bacterial superinfection (like
S. pneumonia
,
H. influenzae
, and
M. catarrhalis
) may occur in 1–2% of adults with community-acquired ARS. Bacterial superinfection occurs more frequently in children (5–10%).

   Who Should Be Suspected?

   Nasal congestion, purulent discharge, middle ear pain or fullness, tenderness over the maxillary sinus, and cough are common signs of uncomplicated ARS.