Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
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        Cryptosporidium spp. antigen test, stool/ feces
      

Here is a Forensic Files episode about the 1993 Milwaukie outbreak that affected 400,000 and killed 100 HERE. Cryptosporidia come from farm animals or human waste and cause cryptosporidiosis diarrhea. The encapsulated phase is acid fast positive when stool smear is stained.

This specific qualitative EIA-type test will ordinarily be performed when the GLCS screening test is positive. The   specimen is (left-over specimen from the GLCS test can be used) stool/feces from rectum or stool sample (on swab, spatula, plastic spoon, etc.) obtained from diaper or "potty"/toilet. This is an immunological test which detects cryptosporidium (CSA) antigen (Ag) which is nearly constantly present in the parasitized patient's feces. So, this is a much better test than stool "wet prep exam" or "stool for O & P". It does not cross-react with antigen from other parasites, and it is stable during routine conditions of specimen acquisition, transport and storage.

Test wells are reagently coated with monoclonal Ab against the parasite Ag. As test sample is exposed to the test-well surface, the attached monoclonal Ab "captures" parasite Ag from the stool (if any be present), forming an immobilized Ag-Ab complex on the well surface. The test well is incubated and then  washed to get rid of any excess unbound Ag. A reagent enzyme conjugate (monoclonal anti-Ag "labeled" with the enzyme horseradish peroxidase) is then added to the test well and the conjugate complex "sticks" to any Ag-Ab complexes lining the well surface (if any be present). Then any excess is washed from the well. The colorless substrate for the enzyme label to react on, TMB, is then added. If any enzyme be attached to the well (onto Ag-Ab complexes), then the TMB "triggers" and turns into a yellow-colored reaction product which can be detected visually or with an spectrophotometer. Test controls are always used to make sure that all components are working.

negative, non-reactive, undetectable test status:

  • indicates a high probability that the patient does not have cryptosporidiosis

  • it is theoretically possible to have such a light parasitization (or to test an incompletely treated case with a very light residual population) and have a "false negative" test result

positive test result:

  • indicates Cryptosporidium spp. parasitization

(Posted May 2006; link added 1 April 2014)

 
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