Parasitology Proficiency Testing Program

GENERAL CRITIQUE FOR 02 February 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

February 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 04-L you reported the correct answer Paragonimus westermani plus Chilomastix mesnili (incorrect) your score would be:

For example: If in sample 04-N you reported Entamoeba histolytica (incorrect) but failed to report Entamoeba coli (correct) your score would be:

QUALITY CONTROL

04-K Participating and referee laboratories agreed that Taenia sp. was the correct answer (99 and 100%). Quality control examination of 4% of this sample revealed an average of 25 ova per coverslip. Also present are rare Giardia duodenalis cysts. Other tests performed included Direct Immunofluorescent Assay and ELISA for Giardia duodenalis and Cryptosporidium sp. which were positive for Giardia and negative for Cryptosporidium. A modified acid-fast stain was also negative.

04-L Participating and referee laboratories agreed that Paragonimus westermani was the correct response (99 and 100%). Quality control examination of 4% of this sample showed an average of 30 ova 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-M 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 normal fecal debris. 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-N Participating and referee laboratories agreed that Entamoeba coli was the correct response (94 and 100%). Quality control examination of 4% of this sample showed cysts every 4-5 100X oil emersion fields. Also present are rare trophozoites. Some cysts are degraded or have stained too dark to be able to see nuclei well.

04-O Participating and referee laboratories agreed that Plasmodium falciparum was the correct response (88 and 100%). Quality control examination of 4% of this sample showed erythrocytes of normal size and staining characteristics. Parasites are present in every 5-8 oil fields. Signet rings, applique´s, and some double chromatin forms are noted.

DIAGNOSTIC CHARACTERISTICS

	The diagnostic stage of the intestinal cestode Taenia sp. is the characteristic egg found in stool. These eggs are yellow-brown, round to oval and measure 35-40 micrometers. They have a thick radially striated shell and contain an oncosphere with visible hooks. Infection occurs when raw or poorly cooked beef or pork containing encysted larvae is ingested. The larvae are digested out of the meat in the stomach and attach to the wall of the small intestine. The adult worms mature in about 5-12 weeks and begin to produce proglottids containing infective eggs. These eggs are passed in the stool to the environment where the cycle is continued.
	The diagnostic stage of Paragonimus westermani is the characteristic egg found in stool or sputum. These eggs are yellow-brown, ovoid, and have a prominent operculum. They measure 80-120 micrometers by 45-70 micrometers and have a thickened shell at the abopercular end. Humans become infected when they ingest uncooked shellfish containing metacercariae. These metacercariae excyst in the duodenum and migrate into the lungs where they mature and release their eggs into the sputum. The eggs are then coughed up and released into the environment or swallowed and passed in the feces.
	Entamoeba coli is distributed worldwide and is nonpathogenic. The trophozoites vary in size from 15-50 micrometers with an average range of 20-25 micrometers. They have a single nucleus that generally has a large diffuse karyosome and irregular peripheral chromatin. The cytoplasm is generally granular and vacuolated. The cysts measure between 10-35 micrometers with an average range of 15-25 micrometers. Most of the cysts noted in this sample were in the 10-15 micrometer size range. The mature cyst has 8 nuclei that have uneven peripheral chromatin and large diffuse karyosomes. Chromatin bars are less common than in Entamoeba histolytica and have pointed ends. Infection occurs by ingesting contaminated food or water.
	Plasmodium falciparum is one of the four species of Plasmodium know to infect humans. It causes the most dangerous and severe form of malaria and is always considered to be a medical emergency. Death may occur rapidly if proper treatment is not started immediately. Its distribution is limited to the tropics, primarily Africa and Asia. P. falciparum invades all ages of RBC's and so the parasitemia can exceed 50%. The usual stages seen in the peripheral blood are rings and gametocytes. Schizogony occurs in the internal organs so it is rare to see other stages although they may be present in cases of severe malaria. The infected RBC's are not enlarged nor do they contain Schüffner's dots. The rings are generally small, and may have one or two chromatin dots. Applique´ forms are also characteristic. Gametocytes are rounded to banana-shaped and contain a single well defined chromatin and coarse rice-grain like pigment.

IMPORTANT REMINDERS

The next Parasitology Proficiency Test is scheduled for June 07, 2004. You are responsible for notifying us before June 14, 2004 if you do not receive your test. Proficiency test results must be postmarked by June 21, 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 Molecular Techniques Wet Workshop will be held in Albany, New York May 17-21, 2004. Registration forms will be sent to all permitted laboratories in March. 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 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. Please continue to submit EDTA whole blood samples with all requests for malaria confirmation so we can validate these new assays and make it 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.