Parasitology Proficiency Testing Program

GENERAL CRITIQUE FOR 03 June 2002

The purpose of the New York State Proficiency Testing Program in the category of Parasitology 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 90% of participating laboratories and/or referee laboratories.

RESULTS OF PARTICIPATING LABS

* PLEASE SEE EXPLANATION IN GRADING AND QC SECTIONS

June 2002 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 '88 Regulations. These state that 90% or more of participating laboratories or referee laboratories must identify the parasite for it to be correct. Similarly, less than 10% of the participating laboratories or referees finding parasites or ova is an incorrect response. Organisms reported by 10-89% of the 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 03-A you reported the correct answer C. sinensis/Opisthorchis sp. plus Chilomastix mesnili (incorrect) your score would be:

If in sample 03-C you reported Endolimax nana (correct) plus Entamoeba histolytica (no penalty) your score would be:

But, If you reported Entamoeba histolytica (no penalty) but failed to report Endolimax nana (correct) your score would be:

If in sample 03-C you reported Endolimax nana (correct) plus Entamoeba coli and Entamoeba hartmanni (both incorrect) your score would be:

* In sample 03-A Giardia duodenalis was graded as "No Penalty" because of a weak positive ELISA result on QC examination.

QUALITY CONTROL

03-A Participating and referee laboratories agreed that Clonorchis sinensis/ Opisthorchis sp. was the correct answer (99 and 100%). Quality control examination of 4% of this sample revealed an average of 23 ova per coverslip. Other tests performed included Direct Immunofluorescent Assay and ELISA for Giardia duodenalis and Cryptosporidium sp. The ELISA was weak positive for Giardia so no penalty was assessed for this response. All other assays were negative for both organisms. A modified acid-fast stain was also negative.

03-B Participating and referee laboratories agreed that Ascaris lumbricoides was the correct response (100%). Quality control examination of 4% of this sample showed an average of 31 fertile and infertile ova per coverslip. Other tests performed included Direct Immunofluorescent Assay and ELISA for Giardia duodenalis and Cryptosporidium sp. which were positive for Cryptosporidium sp. and negative for Giardia duodenalis. A modified acid fast stained smear was also positive for Cryptosporidium sp..

03-C Referee laboratories agreed that Endolimax nana was the correct response (90%). It was also identified correctly by 85% of participating labs. There is an average of 1 cyst per every 3-5 high power fields. 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. Entamoeba histolytica/dispar is also present in significant numbers but was not validated by either participating or referee labs. Referee labs also reported seeing Iodamoeba butschlii so no penalty was assessed for that response.

03-D Participating and referee laboratories agreed that Iodamoeba butschlii (98 and 100%) and Entamoeba coli ( 88 and 90%) were the correct responses. Quality control examination of 4% of this sample showed one Iodamoeba butschlii ( cyst or trophozoite) per every oil field and one Entamoeba coli ( mostly cysts) per every 10-12 oil fields. Blastocystis hominis is also present and was reported by both participating and referee labs (48 and 50%) so no penalty was assessed for reporting this organism.

03-E Participating and referee laboratories agreed that Plasmodium was present (99 and 100%) but failed to reach a consensus on species. Therefore all were given credit. Quality control examination of 4% of this sample revealed at least one organism per every 10-12 oil emersion fields.

DIAGNOSTIC CHARACTERISTICS

	Clonorchis sinensis is a trematode that parasitizes the biliary ducts of humans. Humans become infected when they eat uncooked freshwater fish that contains metacercariae. The metacercariae excyst and travel to the distal bile capillaries where the worms mature. Adult worms deposit eggs in the bile fluid and these are later discharged into the feces. The eggs measure 28-35µm. They are thick shelled, ovoid, and have an operculum with distinct opercular shoulders.
	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 ia 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.
	Endolimax nana is distributed worldwide and is nonpathogenic. The trophozoites measure 6-12µm and have a single nucleus with a large karyosome and no peripheral chromatin. Cysts of Endolimax nana measure 5-10µm, are round to oval, and contain four nuclei. The nuclei of both the cysts and trophozoites can be difficult to see on wet mounts and the addition of iodine is helpful in making the diagnosis.
	Iodamoeba butschlii is distributed worldwide and is nonpathogenic. The trophozoites measure 8-20µm. The nucleus has a large karyosome and no peripheral chromatin. The cytoplasm can be granular and contain many vacuoles. It can be difficult to differentiate the trophozoites of Iodamoeba butschlii from Endolimax nana but the cysts of Iodamoeba are very distinctive. They measure 5-20µm and contain a single nucleus with a large karyosome and no peripheral chromatin. They also have a large well-defined glycogen vacuole.
	Plasmodium vivax is the most common species of malaria to infect humans. It may account for as much as 80% of all malaria cases. It also has the widest distribution. Infected red cells are usually enlarged and stain paler than uninfected ones. They may also contain Schüffner's dots. The trophozoites are generally amoeboid and have a large chromatin. Occasionally cells will contain more than one parasites. Mature Schizonts contain 12-24 merozoites and gametocytes are round and fill the entire cell.

IMPORTANT REMINDERS

The next Parasitology Proficiency Test is scheduled for October 07, 2002. You are responsible for notifying us before October 14, 2002 if you do not receive your test. Proficiency test results must be postmarked by October 21, 2002 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.

NEWS AND NOTES

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 New York State Parasitology Laboratory now has available as an "investigational" tool a Polymerase Chain Reaction(PCR) assay for the detection and species identification of malaria and babesia. Please continue to submit EDTA whole blood samples with all requests for malaria confirmation so we can validate these new assays and make them available as routine diagnostic tests.

The Clinical Parasitology Lab of the NYSDOH now 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.

There will be a full day HANDS ON MALARIA WORKSHOP to be held in conjunction with the Regional ASM meeting October 15th at the Marriot Hotel in Albany. Registration will be limited to 24 participants. Registration forms should be available soon.

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