Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1425 page)

   Use

   Rapid diagnosis of pneumococcal pneumonia. This is a rapid immunochromatographic membrane assay that detects soluble C-polysaccharide cell wall pneumococcal antigen common to all
S. pneumoniae
strains. It is intended, in conjunction with culture results and clinical findings, to aid in the presumptive diagnosis of pneumococcal pneumonia.

   Interpretation

   
Negative result:
Does not exclude
S. pneumoniae
infection.

   
Positive result:
Indicative of pneumococcal pneumonia. A diagnosis of S.
pneumoniae
infection must take into consideration all test results, culture results, and the clinical presentation of the patient.

   Limitations

   S.
pneumoniae
vaccine may cause false-positive results, especially in patients who have received the vaccine within 5 days of having the test performed. This test has sensitivity of 74% and specificity of 94%. Unfortunately, the test has poor specificity in children due to detection of pneumococcal nasopharyngeal colonization. Pneumococcal pneumonia is best diagnosed by sputum culture.

STREPTOZYME, ANTISTREPTOCOCCAL ANTIBODIES, ANTISTREPTOLYSIN O [ASO], ANTI–DNASE-B [ADB]

   Definition

   There are several disease-causing strains of streptococci (groups A, B, C, D, and G), which are identified by their behavior, chemistry, and appearance. Each group causes specific types of infections and symptoms. Group A streptococci are the most virulent species for humans and are the cause of “strep” throat, tonsillitis, wound and skin infections, blood infections, scarlet fever, pneumonia, RF, Sydenham chorea (formerly called St. Vitus dance), and GN. Although symptoms may suggest a streptococcal infection, the diagnosis must be confirmed by tests. The best procedure, and one that is used for an acute infection, is to take a sample from the infected area for culture. However, cultures are useless about 2–3 weeks after initial infection, so the ASO, streptozyme, and ADB screen tests are used to determine if a streptococcal infection is present.

   High titers of these antibodies have been associated with PANDAS (Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcal Infections) and with autism, Tourette syndrome, tic disorder, Parkinson disease, and OCD.

   Streptococcal infections are probably a significant environmental trigger for narcolepsy.

   
Streptozyme: