Parasitology Proficiency Testing Program

GENERAL CRITIQUE FOR 06 October 2003

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 QUALITY CONTROL SECTION

October 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-F you reported the correct answer Hymenolepis nana plus Ascaris lumbricoides (incorrect) your score would be:

If in sample 04-F you reported Hymenolepis nana (correct) plus Trichuris trichiura (no penalty) your score would be:

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

QUALITY CONTROL

04-F Participating and referee laboratories agreed that Hymenolepis nana was the correct answer (99 and 100%). Quality control examination of 4% of this sample revealed an average of 12 ova per coverslip. Also present are rare Trichuris trichiura and rare Entamoeba 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-G Participating and referee laboratories agreed that Srongyloides stercoralis was the correct response (99 and 100%). Also present are rare Trichuris trichiura Quality control examination of 4% of this sample showed an average of 10 larvae per coverslip. 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-H Participating and referee laboratories agreed that Cyclospora cayetanensis was the correct response (95 and 100%). Quality control examination of 4% of this sample showed oocysts in every 1-5 100X oil emersion fields on modified acid-fast. Other organisms are present but only sporozoa should have been reported. Other tests performed included Direct Immunofluorescent Assay and ELISA for Giardia duodenalis and Cryptosporidium sp. which were negative for both organisms.

04-I Participating and referee laboratories agreed that Endolimax nana was the correct response (98 and 100%). Quality control examination of 4% of this sample showed cysts and trophozoites in every 5-10 100X oil emersion fields. Also present are Entamoeba histolytica and Entamoeba hartmanni which were graded as no penalty. Blastocystis hominis is also present but should not have been reported because "All Parasites" was not requested.

04-J Participating and referee laboratories agreed that NO PARASITES SEEN was the correct response (99 and 100%). Quality control examination of 4% of this sample showed erythrocytes of normal size and staining characteristics. Normal blood elements are present and exhibit typical staining characteristics. No inclusions are present.

DIAGNOSTIC CHARACTERISTICS

	Hymenolepis nana also known as the dwarf tapeworm is an intestinal cestode acquired by ingesting eggs from the environment or rarely by ingesting infected beetles. Internal autoinfection is also possible. H. nana is the only human tapeworm that doesn't have an intermediate host and transmission occurs from person to person. It has a worldwide distribution and is more commonly seen in children. The diagnostic stage is the egg recovered in stool. These eggs are spherical, thin shelled, and measure 30 to 47 microns in diameter. They have a six hooked oncosphere with two polar thickenings from which filaments arise. These filaments are visible in the space between the embryo and the outer shell. Eggs of H. nana can be confused with the eggs of Hymenolepis diminuta and careful measurement with a calibrated ocular micrometer is essential. The eggs of H. diminuta are much larger measuring 70-85 microns.
	Strongyloides stercoralis is an intestinal nematode with a very complex life cycle. Infection is acquired when filariform larvae in the soil penetrate the skin and are carried in the blood to the lungs. From the lungs they travel up the trachea and are swallowed. Once in the intestine they develop into mature female worms and begin to produce eggs by parthenogenesis. These eggs, which are rarely seen, hatch in the intestine into rhabditiform larvae. The larvae pass in the feces and develop into male and female worms in the soil where they complete their life cycle. The diagnostic stage is the rhabditiform larvae passed in the stool. They measure 180-380 microns, have a short buccal cavity and a prominent genital primordium shown by the arrow.
	Cyclospora cayetanensis is a coccidian parasites with a worldwide distribution. It is transmitted via the fecal oral route through contaminated food or water. The diagnostic stage is the infective oocyst passed in the stool. These oocysts are acid-fast variable and measure 8-10 microns. They contain two sporocysts, each of which contain two sporozoites. They stain orange with Safranin and are clear to dark pink on modified acid-fast smears. In a wet mounts they appear as non-refractile spheres and will autofluoresce under UV epifluorescence.
	Endolimax nana is distributed worldwide and is nonpathogenic. The trophozoites measure 6-12 microns and have a single nucleus with a large karyosome and no peripheral chromatin. Cysts of Endolimax nana measure 5-10 microns, are round to oval, and contain four nuclei.

IMPORTANT REMINDERS

The next Parasitology Proficiency Test is scheduled for February 02, 2004. You are responsible for notifying us before February 09, 2004 if you do not receive your test. Proficiency test results must be postmarked by February 17, 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

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 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 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.

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