Parasitology Proficiency Testing Program

GENERAL CRITIQUE FOR 07 October 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

October 2002 DISTRIBUTION OF SCORES

ANSWER KEY

TOTAL POSSIBLE POINTS 100

*Unauthenticated-All answers accepted

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-G you reported the correct answer Isospora belli plus Chilomastix mesnili (incorrect) your score would be:

If in sample 03-G you reported Isospora belli (correct) plus Cryptosporidium sp. (no penalty) your score would be:

But, If you reported Cryptosporidium sp. (no penalty) but failed to report Isospora belli (correct) your score would be:

Sample 03-I was unauthenticated so it was not graded and all answers were given credit.

Quality Control

03-F Participating and referee laboratories agreed that Diphyllobothrium latum was the correct answer (100%). Quality control examination of 4% of this sample revealed an average of 12 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.

03-G Participating and referee laboratories agreed that Isospora belli was the correct response (98 and 100%). Quality control examination of 4% of this sample showed an average of 25 oocysts per coverslip. Other tests performed included Direct Immunofluorescent Assay which was positive for Cryptosporium sp. and negative for Giardia duodenalis and ELISA which was negative for both organisms. A modified acid fast stained smear was also positive for Cryptosporidium sp..

03-H Participating and referee laboratories agreed that No Parasites Seen was the correct response (98 and 100%). 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.

03-I Participating and referee laboratories failed to authenticate Blastocystis hominis as the correct answer (86 and 80%) so all answers were accepted. Quality control examination of 4% of this sample showed one cyst per every 3-5 oil fields. Staining quality was variable which may have led to the high number of labs reporting "No Parasites Seen".

03-J Participating and referee laboratories agreed that Trypanosoma cruzi was the correct response (99 and 100%). Quality control examination of 4% of this sample revealed at least one organism per every 10-15 oil emersion fields.

Diagnostic Characteristics

	Diphyllobotrium latum is an intestinal tapeworm acquired by ingesting raw or poorly cooked freshwater fish. The diagnostic stage is the egg recovered in stool. These egge are ovoid and measure 60 to 70µm by 20-35µm. They have an operculum at one end and a small knob at the other. The knob may or may no be visible depending upon the position of the egg. These eggs may be confused with Paragonimus sp. so measurement with a calibrated ocular micrometer is important.
	Isospora belli is usually found in tropical areas. Long oval oocysts are passed in the stool. They measure 20-30µm by 10-20µm. They are easily visualized on wet mounts but are also acid fast. The infective stage is the mature oocyst which contains 2 sporocysts with 4 sporozoites each. The more commonly seen immature oocyst has a single spherical sporont.
	Blastocystis hominis is distributed worldwide and its classification remains unclear. It is for this reason that we ask that you report Blastocystis hominis only when "All Parasites" is requested. Organisms range in size from 6-40µm and are characterized by a large central body with a rim of cytoplasm that contains nuclei and inclusion bodies. On a permanently stained smear the central body takes on a green color while the nuclei and other inclusion bodies stain red. The pathogenicity of this organism is still unresolved.
	Trypanosoma cruzi is the causative agent of the zoonosis Chagas' disease. It is a major health problem in Latin America. The organism is transmitted through the feces of the reduviid bug when it takes a blood meal. Trypomastigotes are detected in the blood on thin and thick smears. They measure approximately 20µm and usually are C or U shaped. The nucleus is located in the middle of the organism and a large kinetoplast is located at the posterior end. A flagellum arises from the kinetoplast and follows the undulating membrane to the anterior end where it projects as a free flagellum. On giemsa stained smears the cytoplasm stains blueish while the nucleus and kinetoplast stain purple or red.

IMPORTANT REMINDERS

The next Parasitology Proficiency Test is scheduled for February 03, 2003. You are responsible for notifying us before February 10, 2003 if you do not receive your test. Proficiency test results must be postmarked by February 17, 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.

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.Remember that the NYS Parasitology Lab only accepts specimens preserved in appropriate fixatives for the test requested.

Please visit 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 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.