Parasitology Proficiency Testing Program

GENERAL CRITIQUE FOR 04 October 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

October 2004 DISTRIBUTION OF SCORES

ANSWER KEY

TOTAL POSSIBLE POINTS 100

* UNAUTHENTICATED-All answers receive 20 points

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-F you reported the correct answer Endolimax nana plus Cyclospora cayetanensis (incorrect) your score would be:

QUALITY CONTROL

05-F Participating and referee laboratories agreed that Endolimax nana was the correct answer (88 and 100%). Quality control examination of 4% of this sample revealed cysts in every high powered field. The cysts measure between 7-10µm are oval and the four nuclei can sometimes be seen as the plane of focus is adjusted . Blastocystis hominis is also present but should not have been reported because "All Parasites" was not requested. 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-G Participating and referee laboratories agreed that Giardia duodenalis was the correct response (100 and 100%). Quality control examination of 4% of this sample showed cysts in every high powered field. The cysts measure between 11-14µm and the four nuclei and filaments are easily seen. 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 stained smear was negative.

05-H Participating and referee laboratories agreed that Clonorchis sinensis/Opisthorchis sp. was the correct response (99 and 100%). Quality control examination of 4% of this sample showed an average of 25 ova per coverslip. The ova measure between 25-30µm and have a prominent operculum. 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 smear was also negative.

05-I Participating and referee laboratories agreed that NO PARASITES SEEN was the correct response (85% and 100%). Quality control examination of 4% of this sample showed many fecal artifacts including leukocytes, yeast, and vegetative matter all of which may be confused with amoeba.

05-J Participating laboratories failed to agree that Loa loa was the correct response (65%). Although referee laboratories did agree that Loa loa was the correct response(80%) this sample was ungraded due to the low number of organisms present. Quality control examination of 4% of this sample showed approximately 3-4 microfilariae on every slide. These microfilariae are sheathed and have nuclei extending to the tip of the tail. The sheath does not stain with giemsa but is still highly visible

DIAGNOSTIC CHARACTERISTICS

	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. The addition of iodine is helpful in making the diagnosis.
	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 10-20µm. They have 2 nuclei, 4 pair of flagella, 2 axonemes, and 2 median bodies. The infective cysts are oval and measure 11-15µm. They contain 4 nuclei usually located at one end, filaments, and median bodies.
	Clonorchis sinensis is a trematode that parasitizes the biliary ducts of humans. Humans become infected when they eat uncooked freshwater fish that contain 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, have an operculum with distinct opercular shoulders, and a knob at the abopercular end.
	White blood cells can sometimes be confused with amoebae. They can be distinguished primarily by examining their nuclei. The ratio of nuclear material to cytoplasm is about 1:1 in polymorphonuclear leukocytes (PMNs) and is about 1:10 in trophozoites of Entamoeba histolytica and 1:3 in cysts. The nuclei of PMNs are also segmented, connected by narrow bands of chromatin. The segments may sometimes appear as separate nuclei but by focusing up and down the connecting strands can usually be seen. Compare the nuclei of the PMN with those of Entamoeba histolytica in the images.
	Loa loa also called the African eye worm, infects humans when they are bitten by infected deer or mango flies. The larvae are deposited into the bite wound and develop into adults within 6-12 months. Adults migrate beneath the conjunctiva or the skin, or through subcutaneous tissues. Years after the initial infection the adults give rise to microfilariae which can be detected in the blood. The microfilariae are sheathed and measure between 250-300µm. They have nuclei that extend all the way to the tip of the tail. Although the sheath does not stain with giemsa it is still clearly visible as shown in the images.

IMPORTANT REMINDERS

The next Parasitology Proficiency Test is scheduled for February 07, 2005. You are responsible for notifying us before February 14, 2005 if you do not receive your test. Proficiency test results must be postmarked by February 22, 2005 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

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.

A Malaria Workshop is scheduled for April 28, 2005 at Weill Medical College of Cornell University, NY, NY. Registration forms will be sent to all permitted laboratories in January. For further information or a registration form call 800-536-NLTN or visit NLTN web site.

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