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Parasitology Proficiency Testing Program

BBPO CRITIQUE FOR 06 June 2005

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.

ANSWER KEY

SAMPLE	CORRECT ANSWERS	POINTS
06B-A	Plasmodium falciparum	20
06B-B	NO PARASITES SEEN	20
06B-C	Plasmodium malariae	20
06B-D	NO PARASITES SEEN	20
06B-E	Plasmodium vivax*	20

TOTAL POSSIBLE POINTS 100

* Unauthenticated

SAMPLE 06B-A

RESULTS OF PARTICIPATING LABS

ORGANISM	NUMBER REPORTED	PERCENT REPORTED	STATUS
Plasmodium falciparum	13/13	100	Correct

QUALITY CONTROL

Participating laboratories agreed that Plasmodium falciparum was the correct response (100%). Quality control examination of 4% of this sample showed infected erythrocytes in every 4-5 oil emersion fields. The infected cells are not enlarged and no stippling was observed. The only stage seen was the ring stage trophozoites. Signet ring, headset, and appliqué forms were all observed. Polymerase Chain Reaction (PCR) analyses for the four species of human malaria were performed. They were negative for Plasmodium vivax, malariae, and ovale and positive for Plasmodium falciparum.

DIAGNOSTIC CHARACTERISTICS

Plasmodium falciparum is one of the four species of malaria 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 in 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. Appliqué forms are also characteristic. Gametocytes are rounded to banana-shaped and contain a single well defined chromatin and coarse rice-grain like pigment.

SAMPLE 06B-B

RESULTS OF PARTICIPATING LABS

ORGANISM	NUMBER REPORTED	PERCENT REPORTED	STATUS
NO PARASITES SEEN	13/13	100	Correct

QUALITY CONTROL

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.

SAMPLE 06B-C

RESULTS OF PARTICIPATING LABS

ORGANISM	NUMBER REPORTED	PERCENT REPORTED	STATUS
Plasmodium malariae	13/13	100	Correct

QUALITY CONTROL

Participating laboratories agreed that Plasmodium malariae was the correct response (100%). Quality control examination of 4% of this sample showed parasites in every 8-10 oil emersion fields. Infected erythrocytes are normal to slightly smaller than normal in size and no stippling is present. The predominant stage seen is the mature trophozoite which exhibits a large chromatin and coarse pigment. Band forms and basket forms were observed as well as an occasional ring. PCR analyses for the four species of human malaria were performed. They were negative for Plasmodium vivax, falciparum, and ovale and positive for Plasmodium malariae.

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.

SAMPLE 06B-D

RESULTS OF PARTICIPATING LABS

ORGANISM	NUMBER REPORTED	PERCENT REPORTED	STATUS
No Parasites Seen	13/13	100	Correct

QUALITY CONTROL

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.

SAMPLE 06B-E

RESULTS OF PARTICIPATING LABS

ORGANISM	NUMBER REPORTED	PERCENT REPORTED	STATUS
Plasmodium vivax	07/13	54	Unauthenticated
Plasmodium ovale	06/13	46	No Penalty

QUALITY CONTROL

Participating laboratories failed to agree that Plasmodium vivax was the correct response (54%). Quality control examination of 4% of this sample showed parasites in nearly every oil emersion field. Cells are enlarged and Schüffner's stippling is present. The parasites are amoeboid and all stages were observed. Pigment was scattered and fine and schizonts contained >16 merozoites. PCR analyses for the four species of human malaria were performed. They were negative for Plasmodium malariae, falciparum, and ovale and positive for Plasmodium vivax.

DIAGNOSTIC CHARACTERISTICS

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. The top two images show Gametocytes of P. vivax and P. ovale. In P. vivax they are round and fill the entire cell unlike P. ovale which are smaller and don't usually fill the entire RBC. Pigment is fine and scattered in P. vivax and much coarser in P. ovale. The next two images show an immature schizont of P. vivax which has greater than 16 developing merozoites in contrast to the schizont of P. ovale which contains only 6-8 merozoites clustered around a single dark mass of pigment.

FEBRUARY DISTRIBUTION OF SCORES

SCORE	NO. OF LABS	PERCENT
100	13	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:

Number of correct responses by lab # Correct Parasites Present + # Lab's Incorrect Answers

X 100

IMPORTANT REMINDERS

The next Parasitology Proficiency Test is scheduled for October 03, 2005. You are responsible for notifying us before October 10, 2005 if you do not receive your test. Proficiency test results must be postmarked by October 17, 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 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 February 05, 2001 test event 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.

A Malaria Workshop is scheduled for September 08, 2005 at the Albany College of Pharmacy, Albany, NY. Registration forms were sent to all permitted laboratories. Registration deadline is August 31, 2005. For further information or additional registration forms 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.