Gastrointestinal Parasite Panels

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Gastrointestinal Parasite Panels Indications for Ordering Gastrointestinal Parasite Panel by PCR 2011150 • Sensitive alternative to traditional, insensitive ova and Aid in the diagnosis of gastrointestinal (GI) infections caused parasite examinations of stool specimens for the by common protozoal pathogens evaluation of GI infections Test Description • Detects o Cryptosporidium hominis, C. parvum Test methodology o Cyclospora cayetanensis Qualitative polymerase chain reaction o Dientamoeba fragilis o Entamoeba histolytica Clinical validation o Giardia lamblia/intestinalis/duodenalis Validated with specimens identified by conventional stool Related tests parasite tests including Cryptosporidium Antigen by EIA 0060045 • Ova and parasite examination • Modified acid-fast stain Entamoeba histolytica Antigen, EIA 0058001 • Giardia, Cryptosporidium, and Entamoeba histolytica Giardia Antigen by EIA 0060048 antigen detection assays Microsporidia by PCR 2011626 • Detects DNA of Encephalitozoon spp (E. intestinalis/E. Tests to Consider hellem/E. cuniculi) and Enterocytozoon bieneusi Typical testing strategy Parasitology Stain by Modified Acid-Fast 0060046 • Stool antigen testing for • Detects Cryptosporidium, Cyclospora, and Cystoisospora o Giardia spp Ova and Parasite Exam, Fecal (Immunocompromised or o Cryptosporidium spp Travel History) 3001662 o E. histolytica • Detects G. duodenalis, E. histolytica, Dientamoeba fragilis, • At least three separate stool specimens, collected on helminth eggs, protozoa, larval worms, and segments of separate days, should be submitted for tapeworms o Ova and parasite examination • Does not specifically detect Cryptosporidium, Cyclospora, o Modified acid-fast stain for coccidian parasites Cystoisospora, or Microsporidia • Often, only ova and parasite examination is ordered on a single specimen Disease Overview o May be inadequate frequency of testing with Incidence inappropriate method to detect pathogen(s) • C. cayetanensis • Gastrointestinal parasite with or without microsporidia by o Clustered outbreaks associated with contaminated food PCR products o Order if GI infection due to protozoal pathogens is o Outbreaks have been occurring recently in higher suspected frequency o Do not order for patients with diarrhea developed . Not associated with foreign travel, but rather, foreign during prolonged hospitalization food products sold domestically Primary tests • C. hominis, C. parvum Gastrointestinal Parasite and Microsporidia by PCR 2011660 o Found in large outbreaks associated with contaminated • Most comprehensive and sensitive alternative to water sources traditional, insensitive ova and parasite examinations of o Can occur year-round when artificial water storage stool specimens for the evaluation of GI infections systems are involved • Includes Gastrointestinal Parasite Panel by PCR and Microsporidia by PCR

• D. fragilis Treatment issues o Has been described as the second most common • Treatment is not indicated for all patients parasitic pathogen after Giardia spp o Not universally effective at curing infections . Difficult to identify using ova and parasite o Treatment is different for each parasite examinations • Most infections are self-limiting  May lead to an underestimate of true prevalence • Spread to close contacts is a concern for several of these • E. histolytica parasites o Typically limited to individual cases, with possible spread to sex partners or close contacts Test Interpretation • G. lamblia/intestinalis/duodenalis Analytical sensitivity o Typically limited to individual exposures to • C. cayetanensis: 80 copies/reaction contaminated water sources in warm-weather months • Cryptosporidium parvum/hominis: 216 copies/reaction • Microsporidia • D. fragilis: 200 copies/reaction o Enteric microsporidiosis in patients with HIV infection • E. bieneusi: 1,600 copies/100 µL stool . ~15% prior to combination antiretroviral therapy • E. histolytica: 100 copies/reaction (cART) • Encephalitozoon spp (E. intestinalis): 440 copies/100 µL . Rates are lower for patients on cART stool o Undetermined incidence in non-HIV populations • Giardia – 960 copies/reaction Symptoms Analytical specificity • Cryptosporidium • No cross-reactivity observed for 48 organisms tested o Watery diarrhea, stomach cramps, nausea, vomiting, fever, dehydration Results • Cyclospora • Detected: detection of protozoal parasites in stool is o Watery diarrhea, loss of appetite, weight loss, cramping, considered diagnostic for infection bloating, gas, nausea, fatigue • Not detected: no protozoal parasites identified • D. fragilis • Inhibited: stool specimens may contain inhibitors of o Asymptomatic or molecular tests o Diarrhea, abdominal pain, loss of appetite, weight loss, o These specimens cannot be resolved nausea, fatigue Limitations • E. histolytica • Due to the periodic shedding of some parasites, a result of o Asymptomatic or “not detected” cannot completely rule out infection with o Mildly symptomatic these parasites . Diarrhea, stomach pain/cramping or o If clinical signs and symptoms persist, an additional o Dysentery specimen for testing may be indicated . Stomach pain, bloody diarrhea, fever o Viral and bacterial gastroenteritis are more common • Giardia than parasitic gastroenteritis and should be considered o Diarrhea, gas, abdominal cramps, nausea, vomiting, as alternative diagnoses dehydration • Asymptomatic infections are known to occur, and • Microsporidia therefore correlation of test results with clinical signs and o Persistent diarrhea symptoms is imperative o Abdominal pain, nausea, vomiting • Panel does not detect Diagnostic issues o Helminths (flatworms, roundworms, and flukes) • Conventional ova and parasite examinations o Nonpathogenic protozoa o Sensitivity depends on the proficiency of the laboratory o Cystoisospora and number of specimens submitted for testing o Microsporidia • Adjunct methodologies, such as modified acid-fast stains . Detected in Gastrointestinal Parasite and and antigen tests, are historically underutilized Microsporidia by PCR • To detect pathogens in the panel, at least seven tests are • Negative result does not rule out traditionally required for maximum o Presence of PCR inhibitors in specimen performance/detection o Assay-specific nucleic acid in concentrations below the level of detection