Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1338 page)

   
Turnaround time:

   Molecular diagnostic, immunodiagnostic assays, and the glutamate dehydrogenase assays: 24 hours

   Cytotoxicity assays: 24–72 hours

   Culture: 96 hours

   Liquid stool specimens collected in clean containers with tight-fitting lids should be transported to the laboratory at room temperature within 2 hours. If transport will be prolonged, the specimen should be held at refrigerator temperature. Do not freeze.

   Interpretation

   
Expected results:
Negative

   Limitations

   The available assays vary somewhat in sensitivity and specificity for diagnosis of
C
.
difficile
disease. The choice of diagnostic methods must take cost, assay performance, turnaround time, and other factors into consideration. Positive
C
.
difficile
test results must be interpreted with caution in infants; toxin may be detected in the stool of healthy infants without signs of diarrheal illness or colitis.

CORYNEBACTERIUM DIPHTHERIAE
CULTURE (RULE OUT)

   Definition and Use

   This culture is used to detect
Corynebacterium diphtheriae
in clinical specimens. It should be considered in patients who present with signs and symptoms consistent with diphtheria, which is caused by local infection, most commonly respiratory or cutaneous infection, or by systemic disease caused by the action of diphtheria toxin, primarily on the heart, central or peripheral nervous system, liver, and kidney. Diphtheria is now uncommon in countries that have implemented widespread vaccination programs against this pathogen.

   
Method:

   Specimens must be inoculated onto special media, including selective, enriched and differential media, for isolation of
C
.
diphtheriae
.