Parasitic diarrhea: It is what it is
Veteran techs all have horror stories about ova and parasite examinations (O&Ps), many (considering the subject “matter” involved) are unprintable. We may have received a zip-locked, rock-hard “sample” or a dirty diaper with an implored request: “Can you at least take a look and see what it might be?” Most diarrheas are self-limiting and non-parasitic in nature, yet the complete O&P has been a staple in laboratory testing since the advent of plastic, reagent-filled transport tubes. The problems remain the same as those affecting much other “classic” testing/transporting a viable specimen — having a trained tech available to process it and performing an accurate microscopic examination. (But even the best lab could not make an ID if the kid was just cutting teeth or got a little to much sun ….)
—Chuck Millstein, MBA, MT(ASCP), CLDir(NCA),
gratefully retired
Why are we still doing the O&P?
Quotation from the College of American Pathologists (CAP): “The Ova and Parasite Examination is no longer considered a test for parasitic diarrhea but for unusual syndromes in travelers and immigrants.”
Times are changing. New technology replaces old methods, so why do we continue to offer the routine ova and parasite examination for the diagnosis of parasitic diarrhea? In the United States, or anywhere in the Northern Hemisphere for that matter, two parasites commonly cause diarrheal illness: Giardia lamblia and Cryptosporidium parvum, and two uncommonly: Entamoeba histolytica and Dientamoeba fragilis.
Many laboratories are steeped in the old tried-and-true ways, not because they are unaware of the new rapid methods. Inertia plays a role. Bringing on change takes effort, including support from directors and cohorts, and you need to look at cost accounting, reimbursement, and coding issues. Knowledge is your most powerful asset.
My laboratory began the slow process of eliminating the O&P and replacing it with the rapid antigen detection method several years ago. We looked at the time it took to perform the full O&P procedure, including filtration, concentration, smear, and stain preparation, and the time spent at the microscope.
We also scrutinized what organisms this method could and could not recover.
And we looked at the rapidly diminishing numbers of technologists qualified to perform parasitology!
We armed ourselves with documented in-house validation studies. We started out by distributing an informational flier. We converted the order from O&P to Giardia and Cryptosporidium antigen methods if the diagnosis on the requisition was diarrhea. We called if there was no comment on the requisition. We offered the O&P only if the patient had diarrhea and had recently been out of the country or was an immigrant (more on that later). We sent these O&Ps to our reference lab; we no longer offered them in-house. We encouraged providers to order the antigen detection methods for G lamblia and C parvum in place of the O&P if they were ruling out parasitic diarrhea.
In the Northern Hemisphere, E histolytica is uncommon, although in some areas of the U.S. it may be more common because of the influx of immigrants into the country and because of the AIDS population. I would recommend the antigen detection triage that includes testing for this organism.
Note: E histolytica — Doing the routine iron hematoxylin or trichrome stain may confuse things because the pathogen E histolytica looks just like the commensal Entamoeba dispar, whereas the antigen-detection method selects out for E histolytica (so they say).
When a provider insisted on the full O&P examination, we would do the rapid antigen method for Giardia and Cryptosporidium and then send the specimen out to our reference lab. Over a period of two years, not one of those specimens came back with any organism not detected by our rapid method. Those specimens from patients who had been out of the country or immigrants with diarrhea came back with Giardia lamblia. Keep in mind that the routine O&P will not detect Cryptosporidium ssp. or any other acid-fast protozoan parasite.
My experience with the uncommon: I spent time in Haiti helping at a medical clinic by doing microbiology and other rudimentary lab tests — very crude, no equipment, relied on my experience to get me by. Part of our complex included an orphanage. There were several puzzling cases of explosive diarrhea among our young patients. It was perplexing in that I had taken with me the EIA (enzyme-immunoassay) cartridges for Giardia and Cryptosporidium. I did saline wet preps on fresh stools looking for telltale signs that would point me in the right direction. I found no motile amoeba, no inflammatory cells to indicate bacterial infection (no equipment or supplies to do culture), and no eggs. I ruled out rotovirus by EIA. I finally just made fecal smears and took them back with me to the U.S. I did an acid-fast stain on them when I got back and found Cyclospora cayetanensis! Who knew? This organism is endemic in Haiti, Nepal, Peru, and Indonesia.
There are exceptions to every rule, and we are aware of the less commonly encountered parasites associated with diarrheal illness. But if we provided for the exception in our analysis of every specimen, the cost to find that rule-breaker would be astronomical. Why not get rid of the O&P, and save yourselves some valuable tech time?
—Colleen K. Gannon, MT(AMT) HEW
the “Nancy Grace” for labs
