Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1361 page)

   Molecular diagnostic techniques provide improved sensitivity for diagnosis of genital infections caused by
N
.
gonorrhoeae
and
C
.
trachomatis
.

   Isolation of a sexually transmitted pathogen from a child must be investigated as a sign of possible abuse.

GIARDIA ANTIGEN DETECTION

   Definition and Use

   The
Giardia
antigen detection test is used for the identification of
Giardia lamblia
in stool specimens. It is used to evaluate diarrheal disease in patients at risk for giardiasis. Giardia EIA has a very high sensitivity (near 100%) and specificity (near 100%) compared with a series of stool O & P examinations.

   
Turnaround time:
24–48 hours.

   Interpretation

   
Expected results:
Negative.

   Limitations

   Several specimens may be required in patients with light infection. Repeat testing improves sensitivity of detection. A series of O & P examinations is recommended in patients with repeatedly negative immunoassays in whom parasitic infection is still suspected.

   
A common pitfall
is submission of the incorrect type of specimen for the assay. To perform immunoassays accurately, the correct specimen type (preserved or fresh) and procedures, as specified in kit instructions, must be followed exactly.

Suggested Readings

CLSI.
Procedures for the Recovery and Identification of Parasites from the Intestinal Tract; Approved Guideline
, 2nd ed. CLSI document M28-A2. Wayne, PA: Clinical and Laboratory Standards Institute; 2005.

Garcia LS.
Diagnostic Parasitology
, 5th ed. Washington, DC: ASM Press; 2007.

GRAM STAIN

   Definition and Use

   Indications: