GM TestParasitology (Intestinal)

Submission Only by Local Health Departments and State Agencies Used for screening refugees, migrant workers, missionary workers, day care workers, or health care workers arriving from countries where parasites are prevalent and for diagnosis of symptomatic persons. The Oregon State Public Health Laboratory uses 5-10 % formalin routinely for concentrating cysts, eggs and larvae of intestinal parasites. In specimens where Entamoeba histolytica cannot be ruled out, or is suspect, both polyvinyl alcohol (PVA) and formalin^* should be submitted. PVA must also be used for liquid stool samples when Giardia or Entamoeba histolytica are of concern.

Number of Specimens to Submit

Collect a first specimen and, when possible, wait for a report before submitting additional specimens. A positive report may negate the need for further specimens before treatment.


In cases of acute illness or negative findings on the first specimen, submit additional specimens collected at 2 to 5 day intervals. Collect a minimum of three to five specimens for a negative diagnosis. If three formalin samples are negative and Giardia or Entamoeba histolytica is still suspect, then submit a PVA sample also.

Negative report(s) do not necessarily "rule out" parasite etiology of suspicious symptoms until other satisfactory diagnosis is made. E. histolytica cysts may not be shed when the parasite is invasive.

Collection Instructions

Use 5-10% formalin for routine or preliminary screening. Also use PVA if active symptoms of amebiasis or giardiasis are apparent (recent onset, 1-5 days). Trophozoites may be present in watery or loose stool. Well mixed PVA specimens should be accompanied by a formalin sample of the same stool.

1. Have stool passed directly into paper collector provided or use "Saran" type plastic sheet across toilet bowl leaving space for urine to pass in front of sheet. Urine contamination of stool is destructive to parasites.

2. Perform a gross examination of the stool for adult parasites, segments, etc. When present, pathological constituents such as blood, mucus, and shreds of epithelium should be selected to increase the chances of successful diagnosis.

3. Do not throw out preservative solution in the bottle.

4. Transfer stool to bottle by means of the paper or plastic spoon provided in the lid of the plastic container. Soft stool is preferable to hard-formed specimen especially for PVA preservation of trophozoites. Dientamoeba fragilis exists only in the trophozoite form and requires ^*PVA for lab diagnosis. Proportions are one part stool to three parts preservative.

5. Mix stool and preservative well. (See Precautions, located at the end of this section.)

6. Screw lid down tightly and secure with masking tape.

7. Label container with patient's name and date collected to avoid identification error.

8. Complete request form. Place collection bottle AND request form into the large mailing container. Pack paper or tissue around the bottle to absorb possible spillage during shipment.

9. Affix proper postage, mail promptly, and adhere to Federal Shipping Regulations.

Precautions

1. Avoid contact of feces with urine or water.

2. Certain drugs and compounds will render stool specimens unsatisfactory for examination. Among these are antidiarrheal compounds (kaolin-pectate, etc.) antibiotics, antacids, bismuth and barium. Specimens used for parasitologic examination should be obtained before these compounds are used or collection must be delayed until the effects have passed (antiparasitical agents, 10 days to 3 weeks; others, 7-10 days).

3. Specimens improperly mixed and/or with improper proportions of stool to preservative will be reported as "unsatisfactory for examination." These specimens may be processed, but the report must be considered incomplete, especially "negative" results. A qualifier will be added to these reports.

4. Basic clinical information may be critical in selecting optimal diagnostic procedures. If the request form lacks this information, the test may be delayed until further information is obtained.

*PVA must be stored at room temperature. Formalin may be stored at room temperature or in the refrigerator (2°C to 5°C).

Reports

Identification is performed Monday through Friday. Turnaround time is 2-7 days.

If additional information regarding testing and/or interpretation of results is needed, contact the General Microbiology section of the Oregon State Public Health Laboratory, 503-229-5885.

References

1. U. S. Dept. of Health, Education, and Welfare/ Public Health Service/ Center for Disease Control, Laboratory Procedures for the Diagnosis of Intestinal Parasites, Dec. 1974; DHEW Publication No. (CDC) 76-8282.

2. U. S. Dept of Health, Education, and Welfare /Public Health Service/ Center for Disease Control, Laboratory Procedures - Amebiasis, Laboratory Diagnosis Part III, 1976; DHEW Publication No. (CDC) 77-8327.