Parasitology Proficiency Testing Program

BBPO Critique for 02 February 2004

The purpose of the New York State Proficiency Testing Program in the category of Parasitology Blood Borne Parasites is to monitor the performance of applicant laboratories in detecting and identifying parasites on blood films.

Sample Preparation and Quality Control

All slides used in this test were prepared and stained by a commercial source. 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:

Quality Control

04B-K Participating laboratories agreed that Plasmodium malariae was the correct response (100%). Quality control examination of 4% of this sample revealed infected erythrocytes in every 4-5 oil fields. The infected cells are normal to smaller than normal in size and exhibit normal staining characteristics. The predominant stages seen are mature trophozoites and gametocytes. Band and basket form trophozoites are also seen.

04B-L Participating laboratories agreed that No Parasites Seen was the correct response (92%). 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.

04B-M Participating laboratories failed to agreed that Plasmodium vivax was the correct response (69%). Quality control examination of 4% of this sample showed infected erythrocytes in every 10-12 oil emersion fields. The infected cells are enlarged and some exhibit Schüffner's stippling. All stages except Schizonts are seen. The chromatin is small and well defined and pigment, where present, is scattered and fine. Because of the lack of laboratory consensus this sample was analyzed by a PCR assay and confirmed to be Plasmodium vivax.

04B-N Participating laboratories agreed that No Parasites Seen was the correct response (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.

04B-O Participating laboratories agreed that Plasmodium falciparum was the correct response (92%). Quality control examination of 4% of this sample revealed infected erythrocytes in every 4-5 oil fields. The infected cells are normal in size and exhibit normal staining characteristics. The only stage seen is the ring stage trophozoite. Signet ring and applique´ forms are present.

Diagnostic Characteristics

	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.
	Plasmodium vivax is the most common species of malaria to infect humans. It may account for as much as 80% of all malaria cases. It also has the widest distribution. Infected red cells are usually enlarged and stain paler than uninfected ones. They may also contain Schüffner's dots. The trophozoites are generally amoeboid and have a large chromatin. Occasionally cells will contain more than one parasite. Mature schizonts contain 12-24 merozoites and gametocytes are round and fill the entire cell.
	Plasmodium falciparum is one of the four species of Plasmodium known 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 seen 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 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 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 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 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.