SPECIMEN COLLECTION PROCEDURES FOR PARASITOLOGY
PRINCIPLE
Accurate clinical diagnosis of intestinal parasite infection is difficult, and laboratory confirmation is usually necessary. Demonstration of the diagnostic stages by direct examination of specimens is the most reliable method of establishing a diagnosis for the majority of parasitic infections, although indirect (serologic) methods are available in a few cases such as trichinosis, echinococcosis, chronic schistosamiasis, or extra-intestinal amebiasis, where the organism is not readily demonstrated.
This laboratory performs only the direct laboratory procedures used in the recovery and identification of intestinal and blood parasites. It is understood that any laboratory procedures employed for the direct examination of parasites is only as reliable as the microscopist who examines the specimen and the satisfactory specimen submitted for examination.
Approximately 100 species of animal parasites can infect the body; about 70 of these are common and considered important. More than half of these can be detected by examination of fecal specimens because they reside in the gastrointestinal tract itself or are so located that they or their progeny finds their way into the alimentary canal. Feces are the most common type of material submitted for parasitologic examination but blood, sputum and urine may be utilized in certain cases.
SPECIMENS COLLECTION, HANDLING AND SHIPMENT
The importance of properly collected specimens for diagnosis cannot be over emphasized. Inadequate, old or improperly preserved samples are usually of little or no value in establishing a diagnosis and may lead to erroneous conclusions.
A specimen kit composed of two screw-cap plastic vials with spoons, one which contains formalin and the other contains PVA, a requisition slip, and mailing container is available from this laboratory. The specimen kit is dated primarily due to the perishable nature of PVA: please do not use outdated kits.
- Fecal specimens should be collected in clean containers or on clean paper and transferred to the specimen vials supplied in the kit. (Feces deposited on soil do not provide a satisfactory specimen since free-living larvae and other contaminants from soil can cause confusion in diagnosis. Feces obtained from toilet bowls are unsatisfactory because there is danger of contamination by organisms and water will destroy trophozoites. Specimens should not be allowed to freeze. Adequate and proper preservation of the fecal sample is essential.)
- The administration of antibiotics or other antiparasitic drugs seriously interfere with the demonstration of amebae, ciliates, flagellates and other parasitic forms. Therefore, the specimen should be collected before the institution of therapy.
- A specimen that cannot be examined immediately should be refrigerated at about 5 degrees Centrigrade and sent to the laboratory as soon as possible.
- The two-vial method for the diagnosis of certain intestinal parasitic diseases is used in this laboratory. The procedure is designed to make a complete diagnosis of parasitic forms involving the intestinal tract other than pinworms.
- The vial with a small black dot contains PVA (polyvinyl alcohol) and is designed to preserve the mobile forms of amebae, ciliates and flagellates which disintegrate shortly after leaving the body.
- The other vial contains formalin and is designed primarily to preserve larvae, etc.
- Using the spoon provided in each vial, add 1 - 2 spoonfuls of feces in the preservative and mix thoroughly.
- Adult worms or proglottids of tapeworms frequently are passed with or without fecal material; these can be placed in the vial containing formalin and sent to the laboratory.
- TIGHTEN CAPS ON VIALS SECURELY.
- Pack the two vials in the mailing container, enclose completed LIMS requisition form or order in LIMS and send to the laboratory.
- NOTE: Because of the intermittent passing of certain parasites from the host, a series of three specimens is recommended. It is preferable to distribute the collection of specimens over several days or a few weeks rather than on successive days.
SPUTUM SPECIMENS
These should be collected in suspected cases of paragonimiasis along with stool specimens. Pulmonary amebiasis and echinococcosis may also be detected by the examination of sputum. The PVA vial should be used for amebiasis; the formalin vial should be used for paragonimiasis and echinococcosis if delayed examination is necessary.
URINE SPECIMENS
Urine specimens, preferably the one passed about or shortly after noon, preserved in formalin is recommended for Schistosoma hematobium. Fresh urine specimens, preferably the first portion of voided urine, should be examined immediately for Trichomonas vaginalis.
PINWORMS
A collection kit can be obtained from the warehouse and is recommended for the detection of Enterobius vermicularis (pinworm). Instructions for obtaining a sample is included in each kit. Specimen should be obtained on the "sticky" side of the collection paddle.
Complete the Test Requisition Form [ Text only version ] or order directly in LIMS. Make sure that slide will not break in transit.
BLOOD
Stained blood films for Malaria should be made from a fresh blood sample without anticoagulant. A slide with a thin smear in the center and a thick drop on one end should be made, allowed to dry thoroughly, placed in a slide container with a completed LIMS requisition form and mailed to the laboratory or an EDTA blood sample can be collected and stored in refrigerator and transported the same day of collection.
Thick and thin smears will be made in the laboratory for examination.
CRYPTOSPORIDIUM, ISOSPORA, CYCLOSPORA (Modified Acid Fast Stain):
Requires specific request, but can be performed on formalin vial from the same specimen as submitted in Ova & Parasite kit (refer to Modified Acid Fast Stains).
RESULTS
The expected turnaround time is as follows:
| Ova and Parasites | 2-4 days after receipt in lab |
| Pinworm | 1-2 days after receipt in lab |
| Cryptosporidium | 2-4 days after receipt in lab |
| Malarial Smear | 1-2 days after receipt in lab |
REJECTION
Samples will be rejected if they are:
- Unlabeled - All specimens MUST have a unique patient identifier.
- Insufficient in Quantity - No specimen received, no specimen in container, or insufficient specimen to perform testing.
- Improperly Preserved - Specimens for Ova & Parasite must be received in both PVA and Formalin transport tubes.
- Damaged - Specimen leaked or broken in transit.
- Too Old - Preserved samples greater than 7 days old are unreliable specimens for testing. Blood specimens more than 24 hrs old will not be accepted.
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