- 1.1 Parasite Classification |
- 1.2 Body Site, Specimens, Procedures, Parasites, Comments |
- 1.3 STAT Testing in Parasitology |
- 1.4 Test Issues and Reports: Computer Report Comments|
- 1.5 Rapid Diagnostic Testing
- 2.1 Stool Testing Order Recommendations |
- 2.2 Fecal specimens for parasites: options for collection and processinga2 |
- 2.3 Preservatives used for Stool Specimens
- 3.1 Body Sites and Specimen Collection | - 3.2 Body sites and the most common parasites recovered | - 3.3 Body Site, Specimens and Recommended Stain | - 3.4 Examination of tissues and body fluids | - 3.5 Parasitic Infections: Clinical Findings Healthy/Compromised Hosts | - 3.6 Microscope Calibration | - 3.7 Serologic, Antigen, and Probe Tests for Parasite Diagnosis
- 4.1 Protozoa: Intestinal Tract, Urogenital System: Key Characteristics | - 4.2 Tissue Protozoa: Characteristics |
- 4.3 Tips on Performance of Fecal Immunoassays for Intestinal Protozoa
5.1 Helminths: Key Characteristics | 5.2 Helminth Parasites Associated with Eosinophilia
6.1 Reference Laboratory for Parasite Blood Testing | 6.2 Parasites Found in Blood: Characteristics
7.1 Malaria (5 Species) (2 P. ovale subspecies) | 7.2 Malaria (5 Species, Images) | 7.3 Rapid Malaria Testing (BinaxNOW Malaria Test) | 7.4 Malaria Parasitemia Method |
7.5 Malaria Parasitemia Interpretation
- USE OF A REFERENCE LABORATORY FOR PARASITE BLOOD DIAGNOSTIC
TESTING (Including the Binax Rapid Test and Report Comments)
- HELMINTH PARASITES ASSOCIATED WITH EOSINOPHILIA |
- Histology: Staining Characteristics - Table 1 |
- Histological Identification of Parasites - Table 2 |
- Microscope Calibration |
- Figures for Histology Identification Table 2 |
Due to the frequent lack of understanding of the clinical relevance of test result reports, it is recommended that canned comments (pre-agreed-upon wording of test report comments) be used to clarify report results. Not only does this approach provide information required for understanding the clinical relevance of such reports, but also it provides educational information for the clinicians receiving the reports. The following examples can be used as provided or can be modified to fit certain institutional or laboratory reporting formats currently in use. Based on laboratorian general consensus, the use of canned comments is recommended in lieu of free-text comments, particularly when report comment statistical analyses are required. This procedure is adapted from Appendix 1 in Garcia LS. Diagnostic Medical Parasitology, 6th ed. ASM Press, Washington, DC. It will be important to check the emergency department, as well as external laboratories, for possible computer report length limits. Based on serviced clients and/or institutions, consultation with these accounts are recommended.
Submission of stool specimens |
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Result or situation |
Report comment(s) |
Interpretation discussion |
Submission of a single stool specimen for ova-and-parasite examination |
One stool specimen is not sufficient for the recovery of intestinal parasites (only a 50% recovery); 2 specimens are recommended, while 3 offers the best chance of organism recovery (approximately >95% recovery) |
While 3 specimens collected over a 10-day period is the best approach, receipt of 2 specimens is acceptable |
Submission of 2 stool specimens for ova-and-parasite examination |
Although submission of 2 stool specimens is acceptable, 3 specimens collected over a 10-day period provide the best approach for organism recovery. |
While 2 specimens are now considered acceptable, 3 specimens will allow the most complete percentage recovery of intestinal parasites present. |
Examination of fecal specimens |
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Result for ova-and-parasite examination |
Report comment(s) |
Interpretation discussion |
No parasites seen |
Antibiotics such as metronidazole or tetracycline may interfere with the recovery of intestinal parasites, particularly the protozoa. |
If a patient is symptomatic and intestinal parasites are suspected, this comment may be helpful for the physician, particularly if the patient has received any of these antibiotics. |
Yeasts, budding yeasts, and/or pseudophyhae (report if moderate, many, or packed) |
Reports of yeasts may or may not be clinically relevant due to possible specimen handling delays prior to fixation. |
Some laboratories do not report yeast due to potential interpretation errors; they may call the physician directly. Because yeasts can continue to grow within the stool prior to fixation, the results from the permanent stained smear may or may not be clinically relevant. Quantitate if moderate, many, or packed. Some laboratories prefer to discuss this finding with the clinician rather than reporting via the standard reporting process. |
Entamoeba histolytica |
Pathogenic; cause of amebiasis |
Result based on presence of ingested RBCs within the trophozoite cytoplasm and/or a positive result using the fecal immunoassay specific for the pathogen Entamoeba histolytica and/or a positive result using molecular testing for E. histolytica |
Result for ova-and-parasite examination |
Report comment(s) |
Interpretation discussion |
Entamoeba histolytica/E. dispar group |
Differentiation between the pathogen Entamoeba histolytica and the nonpathogen Entamoeba dispar is not possible based on organism morphology; if ingested RBCs are NOT seen, unable to differentiate the two organisms OR |
A fecal immunoassay specific for the pathogen, Entamoeba histolytica, can be performed on fresh stool to separate out E. histolytica and E. dispar |
Differentiation of E. histolytica from E. dispar |
To determine the presence or absence of Entamoeba histolytica, submit a fresh stool specimen. |
The fecal immunoassay specific for Entamoeba histolytica requires fresh or frozen stool for testing. |
In some cases, a specimen received in Cary-Blair medium is acceptable; check package insert. |
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Blastocystis spp. is recommended |
Blastocystis spp. contains approximately 17 different subtypes, none of which can be differentiated on the basis of organism morphology; some subtypes have been found to cause symptoms and some have not. If no other pathogens are found, Blastocystis may be the cause of patient symptoms |
Until there are testing options to differentiate between the subtypes, it is important that the physicians know that some subtypes of Blastocystis may cause symptoms. Quantitate these organisms (rare, few, moderate, many, packed). |
Report comments are highly recommended, particularly if the term Blastocystis hominis rather than Blastocystis spp. is used. |
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Blastocystis spp. is recommended |
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Result for ova-and-parasite examination |
Report comment(s) |
Interpretation discussion |
Giardia lamblia (G. duodenalis, G. intestinalis) Giardia duodenalis Giardia intestinalis |
Pathogenic |
If fecal immunoassays are performed, the testing of two separate stools (collected at least 1 day apart) is recommended before the patient is considered negative. The testing of two stools is not required for Cryptosporidium spp. |
Entamoeba hartmanni Entamoeba coli Entamoeba moshkovskii Entamoeba bangladeshi Endolimax nana Iodamoeba büetschlii Chilomastix mesnili Pentatrichomonas hominis Enteromonas hominis Retortamonas intestinalis Trophozoites and/or cysts |
Nonpathogenic; treatment not recommended; however, recovery of these organisms indicates that the patient has ingested something contaminated with fecal material (same infectivity route for pathogens); continued research may require revision of nonpathogenic vs pathogenic classifications. |
It is important to report nonpathogens; the patient may be infected with one or more pathogens not yet found. |
Result for ova-and-parasite examination |
Report comment(s) |
Interpretation discussion |
Microsporidia (fecal and urine specimens) |
The report would indicate “Microsporidian spores present” |
These are the two most likely organisms present; these comments are very helpful, especially in indicating that the two organisms cannot be identified to the genus or species levels on the basis of calcofluor white or modified trichrome-stained smears. |
Enterocytozoon bieneusi Encephalitozoon intestinalis |
“Probably Enterocytozoon bieneusi or Encephalitozoon intestinalis or both; these tend to disseminate from the GIa tract to the kidneys. Identification to the genus/species level not possible from stained smears.” |
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a GI, gastrointestinal. |
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Examination of blood specimens |
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Result |
Report comment(s) |
Interpretation discussion |
No parasites seen |
The submission of a single blood specimen will not rule out malaria; submit additional bloods every 4–6 h for 3 days if malaria remains a consideration |
It is important to make sure the physician knows that examination of a single blood specimen will not rule out malaria. Often an alternate suspected diagnosis is determined based on additional laboratory results. Some recommend a longer time frame between blood draws (12-24 hr). |
Plasmodium spp. seen |
Unable to rule out Plasmodium falciparum or Plasmodium knowlesi |
Since P. falciparum and P. knowlesi cause the most severe symptoms, it is important to let the physician know that these species have NOT been ruled out. |
Plasmodium spp. seena |
No gametocytes seen |
It is important when reporting Plasmodium spp. to indicate the presence or absence of gametocytes; these findings will influence therapy and/or issues of transmission. The approach to the patient will also vary, depending on the geographic area and Plasmodium spp. detected |
Plasmodium spp., possible mixed infection |
Unable to rule out Plasmodium falciparum or Plasmodium knowlesi |
Since P. falciparum and P. knowlesi cause the most severe symptoms, it is important to let the physician know that these species have NOT been ruled out. Consider PCR for identification to species. |
Plasmodium vivax |
Sequelae from this infection may be more serious than once suspected. |
Increasing reports of clinical severity with complicated and lethal cases have modified the perception that infection with P. vivax is benign. |
Result |
Report comment(s) |
Interpretation discussion |
Plasmodium malariae or P. falciparum |
Unable to rule out Plasmodium knowlesi; confirm travel history to Malaysia or neighboring areas |
If the patient has traveled to the area where P. knowlesi is endemic, it may be impossible to differentiate between P. falciparum (rings only), P. malariae (band forms), and P. knowlesi. Consider PCR for identification to species. |
Negative for parasites using automated hematology instruments |
Automated hematology instruments will not detect low malaria parasitemias seen in immunologically naïve patients (travelers) |
Patients who have never been exposed to malaria (immunologically naïve) will become symptomatic with very low parasitemias that will not be detected using automation (0.001 to 0.0001%) |
Negative Plasmodium rapid test (BinaxNOW rapid test, FDA cleared)b |
This test is most sensitive at a parasitemia of 0.1% (>5,000/μl) for P. falciparum and P. vivax. Many patients who have never been exposed to malaria (immunologically naïve) will become symptomatic with very low parasitemias that will not be detected using the rapid malaria test (BinaxNOW). |
It is VERY IMPORTANT to remember that many travelers who have never been exposed to malaria (immunologically naïve) will become symptomatic with very low parasitemias that will not be detected using the rapid malaria test (BinaxNOW). |
If negative, then it is mandatory that STAT thick and thin blood films be prepared, examined, and reported. |
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If positive, then confirmation of the Plasmodium spp. should be obtained. |
Additional testing required for identification confirmation. |
Microscopic and/or molecular confirmation may be required. |
a It is important to specify the presence or absence of gametocytes. The failure of conventional anti-malarials to clear circulating mature gametocytes may allow persisting malaria transmission in the week(s) following treatment. The laboratory report should specify whether or not gametocytes were seen in the stained blood films.
b NOTE: Use of the BinaxNOW (Abbott) malaria rapid test may help detection of mixed infections (STAT test). This test is FDA cleared, and the external malaria control is now also available (BinaxNOW Malaria Product Fact Sheet Test Kit & Positive Control). However, if the test is negative, thick and thin blood film examination is mandatory (STAT).