Parasitology Proficiency Testing Program

GENERAL CRITIQUE FOR 02 June 2003

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

* SEE QUALITY CONTROL SECTION

June 2003 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 04-A you reported the correct answer Necator americanus plus Ascaris lumbricoides (incorrect) your score would be:

If in sample 04-A you reported Necator americanus (correct) plus Trichuris trichiura (no penalty) your score would be:

But, If you reported Trichuris trichiura (no penalty) but failed to report Necator americanus (correct) your score would be:

QUALITY CONTROL

04-A Participating and referee laboratories agreed that Necator americanus was the correct response (99 and 100%). Quality control examination of 4% of this sample revealed an average of 20 ova per coverslip. Also present are rare Trichuris trichiura which were seen by 82% of participating labs and by 70% of referee labs. Because this organism was not seen in every vial examined for quality control by both the NYS Parasitology Laboratory and the suppling vender this response was graded as no penalty. 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.

04-B Participating and referee laboratories agreed that Fasciola hepatica/Fasciolopsis buski was the correct response (93 and 100%). Quality control examination of 4% of this sample showed an average of 16 ova per coverslip. Other tests performed included Direct Immunofluorescent Assay and ELISA forGiardia duodenalis and Cryptosporidium sp. which were negative for both organisms. A modified acid fast stain was also negative.

04-C Participating and referee laboratories agreed that Giardia duodenalis was the correct response (99 and 100%). Quality control examination of 4% of this sample showed cysts in every 1-5 100x oil emersion fields. Other tests performed included Direct Immunofluorescent Assay and ELISA for Giardia duodenalis and Cryptosporidium sp. which were positive for Giardia duodenalis. and negative for Cryptosporidium sp. A modified acid-fast stain was also negative.

04-D Participating and referee laboratories agreed that Dientamoeba fragilis was the correct response(89 and 100%). Quality control examination of 4% of this sample showed trophozoites in every 2-5 100x oil fields. The majority of the organisms contain two nuclei but an occasional uninucleated trophozoite is present

04-E Participating and referee laboratories agreed that Plasmodium malariae was the correct response (94 and 100%). Quality control examination of 4% of this sample revealed at least one organism per every 5-6 100x oil emersion fields. Primary stages are ring forms, growing trophozoites and gametocytes. Infected red blood cells were not enlarged and showed normal staining characteristics.

DIAGNOSTIC CHARACTERISTICS

	Necator americanus (Hookworm) infection occurs in warm moist areas through skin penetration of filariform larvae from the soil. The larvae migrate through the heart and lungs, are swallowed, and take up residence in the small intestine where the adults mature. The diagnostic stage is the egg passed in stool. They are oval and measure approximately 60 X 40 microns. They have a thin shell with a space between the shell and the developing embryo. Development is usually at the 8 to 32 cell stage. These eggs are indistinguishable from those of Ancylostoma duodenale.
	Fasciola hepatica is a liver trematode with a worldwide distribution. It is extremely rare in the United States. Humans become infected by eating uncooked aquatic plants containing metacercariae from the intermediate snail host. These metacercariae excyst in the duodenanum and migrate to the liver. Once the larvae enter the bile ducts they mature and begin to lay eggs which are the diagnostic stage. The eggs are very large measuring 130-150 microns by 60-90 microns. They are thin shelled and have an operculum. Although these eggs are similar in appearance to Paragonimus westermani they are easily distinguished by size.
	Giardia duodenalis is the most commonly diagnosed flagellate in humans. It has a worldwide distribution and is more prevalent in children than in adults. Trophozoites are pear shaped and measure 10-20 microns. They have 2 nuclei, 4 pair of flagella, 2 axonemes, and 2 median bodies. The infective cysts are oval and measure 11-15 microns. They contain 4 nuclei usually located at one end, filaments, and median bodies.
	Dientamoeba fragilis is distributed worldwide and has been reclassified as a flagellate rather than an amoeba. There is no know cyst stage. Trophozoites are either uni- or bi-nucleated. Uni-nucleate organisms are easily confused with Endolimax nana. The nuclear chromatin is often fragmented and no peripheral chromatin is seen. Amoeboid in shape these flagellates measure between 5-15 microns with a typical range of 10-12 microns. The cytoplasm is finely granular and may contain vacuoles.
	Plasmodium malariae is the least common species of malaria to infect humans, and is sporadic in distribution. It tends to infect older red blood cells and so the parasitemia is often low. The ring stage is short lived so it is not usually seen. The most common stages seen are mature trophozoites and schizonts. The infected cells are not enlarged and may actually be smaller than uninfected cells. There is no stippling. The trophozoites are not amoeboid and often appear as compact rounded or band forms. The schizonts contain 6-12 merozoites usually arranged in a rosette although they may be in an irregular cluster.

IMPORTANT REMINDERS

The next Parasitology Proficiency Test is scheduled for October 06, 2003. You are responsible for notifying us before October 13, 2003 if you do not receive your test. Proficiency test results must be postmarked by October 20, 2003 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 www.wadsworth.org/labcert/clep/ProgramGuide/WebGuide.pdf.

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 February 05, 2001 test event 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. Please continue to submit EDTA whole blood samples with all requests for malaria confirmation so we can validate this new assay and make it available as routine diagnostic test.

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. 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.

There will be a Molecular Workshop held in Albany on Monday November 3, through Friday November 7,2003. More information and registration forms will follow.

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