Parasitology Proficiency Testing Program

GENERAL CRITIQUE FOR 07 June 2004

The purpose of the New York State Proficiency Testing Program in the category of Parasitology General is to monitor the performance of applicant laboratories in detecting and identifying parasites in fecal emulsions, fecal smears, and blood films.

SAMPLE PREPARATION AND QUALITY CONTROL

All emulsions and slides used in this test were prepared by a commercial source. The emulsions were dispensed into the vials from pools which were continuously mixed during the loading process. Numerous samples of each test specimen were selected at random by the Parasitology Unit of the David Axelrod Institute for Public Health, and were checked to confirm their contents. Extensive quality control tests were also conducted by the supplying vendor and a detailed quality control report was submitted to the New York State Parasitology Laboratory for inspection and verification. Samples were authenticated by 80% of participating laboratories and/or referee laboratories.

RESULTS OF PARTICIPATING LABS

June 2004 DISTRIBUTION OF SCORES

ANSWER KEY

TOTAL POSSIBLE POINTS 100

GRADING

The answer key was derived from the response of all participating laboratories as per CLIA Regulations,Part 493, Subpart I, Section 493.917. These regulations can be viewed at www.phppo.cdc.gov These regulations state that 80% or more of participating laboratories or referee laboratories must identify the parasite for it to be correct. Similarly, less than 20% of the participating laboratories or referees finding parasites or ova is an incorrect response. Organisms reported by 20-80% of the participating laboratories or referees are "Unauthenticated", and are not considered for grading.

Each sample has a maximum value of 20 points. Credit is given according to the formula:

For example: If in sample 05-A you reported the correct answer Diphyllobothrium latum plus Ascaris lumbricoides (incorrect) your score would be:

If in sample 05-D you reported Entamoeba hartmanni (no penalty) but failed to report Entamoeba histolytica (correct) your score would be:

If in sample 05-D you reported Entamoeba hystolytica (correct) and Entamoeba hartmanni (no penalty) your score would be:

QUALITY CONTROL

05-A Participating and referee laboratories agreed that Diphyllobothrium latum was the correct answer (99 and 100%). Quality control examination of 4% of this sample revealed an average of 15 ova per coverslip. The ova measured between 65-70µm were oval and had an operculum. The abopercular knob is also visible on most of the eggs. No other organisms were observed. Other tests performed included Direct Immunofluorescent Assay and ELISA for Giardia duodenalis and Cryptosporidium sp. which were negative for both organisms. A modified acid-fast stain was also negative.

05-B Participating and referee laboratories agreed that Cryptosporidium sp. was the correct response (98 and 100%). Quality control examination of 4% of this sample showed an average of 1 oocyst per every 8-10 oil emersion fields on a modified acid-fast stained smear. The oocysts are round and measure 4-5µm. They stain light pink to intense fuschia. Other tests performed included Direct Immunofluorescent Assay and ELISA for Giardia duodenalis and Cryptosporidium sp. which were positive for both organisms. Because "Sporozoa Only" was requested the Giardia duodenalis should not have been reported.

05-C Participating and referee laboratories agreed that Ascaris lumbricoides was the correct response (99 and 100%). Quality control examination of 4% of this sample showed an average of 25 ova per coverslip. Most of the eggs seen were fertile and showed typical mammillation. Infertile eggs are also present. Other tests performed included Direct Immunofluorescent Assay and ELISA for Giardia duodenalis and Cryptosporidium sp. which were negative for both organisms.A modified acid-fast stain was also negative.

05-D Participating laboratories agreed that Entamoeba histolytica was the correct response (80%). 30% of the referee laboratories also reported seeing Entamoeba hartmanni so this responce was graded as no penalty. Quality control examination of 4% of this sample showed cysts and trophozoites every 8-10 100X oil emersion fields. The cysts measure 8-15µm, have 4 nuclei, and blunt or rounded chromatoid bodies. Some cysts have stained too dark to be able to see the nuclei well. The trophozoite measure 12-20µm and contain 1 nucleus with a small, distinct, centrally located karyosome.

05-E Participating and referee laboratories agreed that Trypanosoma cruzi was the correct response (99 and 100%). Quality control examination of 4% of this sample showed parasites in every 8-10 100x oil emersion fields. The parasites are variable in size and both stubby and elongated forms are present. They have a centrally located nucleus and a large prominent kinetoplast.

DIAGNOSTIC CHARACTERISTICS

	Diphyllobothrium latum is an intestinal tapeworm acquired by ingesting raw or poorly cooked freshwater fish. The diagnostic stage is the egg recovered in stool. These egge are ovoid and measure 60 to 70µm by 20-35µm. They have an operculum at one end and a small knob at the other. The knob may or may not be visible depending upon the position of the egg. These eggs may be confused with Paragonimus sp. so measurement with a calibrated ocular micrometer is important.
	Cryptosporidium sp. has become one of the most important opportunistic infections seen in the immunocompromised patient. This coccidian parasite is spread through contaminated food or water. The diagnostic stage is the oocyst passed in the stool. On a modified acid-fast stained smear these oocyst measure 4-5µm and stain pale to deep pink. It is sometimes possible to see the 4 sporozoites within the oocyst. Other methods of diagnosis include immunoassays and immunofluorescent stains.
	Ascaris lumbricoides is one of the most common intestinal nematode infections of man. It is most prevalent in warm moist climates but can also be found in cooler areas. Infection is acquired when embryonated eggs in contaminated soil are ingested. The fertilized eggs are round to oval, mammillated,, and golden brown in color. They measure 45-75µm by 35-50µm. Occasionally they may lose their outer mammillated layer. Infertile eggs are larger, less broad, and have thinner shells. They measure 85-90µm by 43-47µm.
	Entamoeba histolytica/dispar is distributed worldwide but is more prevalent in the tropics and subtropics. The trophozoites vary in size from 10-60µm with an average size of 15µm. They have a single nucleus that generally has a small centrally located karyosome. The peripheral chromatin is usually smooth and evenly distributed. The cysts measure between 8-15µm with an average size of 10µm. The mature cyst has 4 nuclei while the immature cyst can have 1 or 2. Chromatin bars are common and have blunt or rounded ends. Infection occurs by ingesting contaminated food or water. In contrast the cysts and trophozoites of E.hartmanni are much smaller. It is common to see organisms measuring 4-8µm. Again careful measurement by a calibrated ocular micrometer is needed.
	Trypanosoma cruzi is the causative agent of the zoonosis Chagas' disease. It is a major health problem in Latin America. The organism is transmitted through the feces of the reduviid bug when it takes a blood meal. Trypomastigotes are detected in the blood on thin and thick smears. They measure approximately 20µm and usually are C or U shaped. The nucleus is located in the middle of the organism and a large kinetoplast is located at the posterior end. A flagellum arises from the kinetoplast and follows the undulating membrane to the anterior end where it projects as a free flagellum. On giemsa stained smears the cytoplasm stains blueish while the nucleus and kinetoplast stain purple or red.

IMPORTANT REMINDERS

The next Parasitology Proficiency Test is scheduled for October 04, 2004. You are responsible for notifying us before October 11, 2004 if you do not receive your test. Proficiency test results must be postmarked by October 18, 2004 or you will receive a zero. These requirements are clearly stated in your NYS Proficiency Testing Handbook provided by the NYS Clinical Laboratory Evaluation Program or can be accessed via the internet at http://www.wadsworth.org/labcert/clep/ProgramGuide/WebGuide.pdf

NEWS AND NOTES

A Malaria Workshop will be held in the fall of 2004. Registration forms will be sent to all permitted laboratories. For further information or a registration form call 800-536-NLTN or visit NLTN web site.

Policy changes made by the Clinical Laboratory Evaluation Program now allow for the CQ holder for a particular category to sign the attestation statement instead of the Laboratory Director. Starting with the test event of February 05, 2001 we will now accept Director's and/or CQ holder's signatures on the attestation statement.

The Clinical Parasitology Lab of the NYSDOH offers two mailing kits for the submission of specimens. One kit contains vials of PVA and Formalin and the other does not. These kits can be ordered by calling 518-474-4175 and requesting kit DOH-2117. Please be sure to specify whether you need preservatives or not.Remember that the NYS Parasitology Lab only accepts specimens preserved in appropriate fixatives for the test requested.

Please check out our website at: http://www.wadsworth.org/parasitology/index.htm.. You can access information about our program, the current answer key and critique, past critiques, and information about upcoming workshops. You can also find links to related sites, contact information, and answers to frequently asked questions.

Beginning with the next test event scheduled for October 2004 we will no longer routinely mail out critiques with the result reports. Parasitology critiques are available on the website at the above address. Critiques have been available in this format since June 2002. If you do not have access to the internet you can request a paper copy by calling Jill Ennis at 518-474-4177 or E-mail: jxe02@health.state.ny.us .

Web site questions or comments or to request a different file format (pdf.,doc.,wpd.) contact:
E-mail: Parasit@wadsworth.org.