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2013 PARASITOLOGY WORKSHOP

2013 PARASITOLOGY WORKSHOP . LYNNE S. GARCIA, MS, FAAM, CLS, BLM Diagnostic Medical Parasitology Workshop 2013 UPDATE – QUIZ PART 7 ORGANISM IDENTIFICATIONS, KEY QUESTIONS SPONSORED BY MEDICAL CHEMICAL CORPORATION www.med-chem.com. ORGANISM # 1. 2.

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2013 PARASITOLOGY WORKSHOP

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  1. 2013 PARASITOLOGY WORKSHOP LYNNE S. GARCIA, MS, FAAM, CLS, BLM Diagnostic Medical Parasitology Workshop 2013 UPDATE – QUIZ PART 7 ORGANISM IDENTIFICATIONS, KEY QUESTIONS SPONSORED BY MEDICAL CHEMICAL CORPORATION www.med-chem.com

  2. ORGANISM # 1 2 Duodenal Fluid, Modified Trichrome Stain General name is acceptable.

  3. ORGANISM # 2 Stool smear stained with Wheatley’s Trichrome stain. Give genus, species, stage names 3

  4. QUESTION 1 Is it good laboratory practice to accept 2 (rather than 3) stools for the O&P examination? Why or why not? 4

  5. ANSWER 1 • Three stool specimens is more accurate, but many laboratories feel organism recovery with 2 stools is acceptable. Percent recovery varies from ~80% to over 95% with the submission and examination of two stool specimens. A single stool specimen is only about 50% accurate. In one study, they found the following increases examining the third stool: Hiatt, et al. (Am. J. Trop. Med. Hyg. 53:36-9, 1995) • Yield increased 22.7%: Entamoeba histolytica • Yield increased 11.3%: Giardia lamblia • Yield increased 31.1%: Dientamoeba fragilis 5

  6. ORGANISM # 3 Fluorescence immunoassay. What are the two structures? Use genus, species names 6

  7. ORGANISM # 4 7 Blood Stain Name genus and species What’s the clue?

  8. QUESTION 2 When selecting a single vial stool fixative, what questions should be asked? What are Universal Fixatives? 8

  9. ANSWER 2 Can one perform a concentration, permanent stained smear, special stains for the coccidia and microsporidia, and/or fecal immunoassay procedures from the specimen received in that vial (Universal Fixative)? What stains work best with that particular fixative? TOTAL-FIX contains NO mercury, NO formalin, and NO PVA. 9

  10. ORGANISM # 5 Stool smear stained with Wheatley’s Trichrome stain. Name genus, species, and stage 10

  11. ORGANISM # 6 11 Blood Stain; Name Genus; What is the structure within the circle called? Is it always seen? O

  12. ORGANISM # 7 Blood Stain What is general term for structures? Name genus and species (bone marrow). 12

  13. ORGANISM # 8 Blood Stain; name genus, species 13

  14. QUESTION 3 What is PVA (stool adhesive)? Does it work like albumin? Does every fixative require one or the other? 14

  15. ANSWER 3 PVA stands for polyvinyl alcohol, a plastic powder/resin that is incorporated into the liquid fixative (Schaudinn’s or other fixatives) and serves as an adhesive to “glue” the stool material onto the slide. PVA itself has no preservation capability and is inert in terms of fixation, just like albumin. TOTAL-FIX requires no adhesive (PVA or albumin). 15

  16. ORGANISM # 9 Blood Stain Name genus, species and common name of disease What’s a clue? 16

  17. ORGANISM # 10 Blood Stain Genus, species 17

  18. ORGANISM # 11 Stool smear stained with Wheatley’s Trichrome stain. Genus, species 18

  19. ORGANISM # 12 Modified Trichrome Stain General term for organisms 19

  20. QUESTION 4 What are some of the immunoassay options available for stool protozoa? How do they rank in terms of sensitivity and specificity? 20

  21. RESPONSE 4 All of the fecal immunoassay test formats (FA, EIA, Rapids) are comparable in terms of sensitivity and specificity. Selection of a particular method depends on work flow and the number of test requests and personal preference of that particular laboratory. 21

  22. ORGANISM # 13 Stool smear stained with Wheatley’s Trichrome stain. Name genus, species, and stages 22

  23. ORGANISM # 14 Blood Stain; genus, species 23

  24. QUESTION 5 If Plasmodium falciparum parasites are in the capillaries, why not do a finger stick, rather than a venipuncture? What is the best anticoagulant to use for blood specimens? When should blood specimens be drawn for a suspect malaria diagnosis? 24

  25. ANSWER 5 The capillaries tend to be in the deep tissues (spleen, liver, bone marrow), so a finger stick sample is no more likely to be positive than a venipuncture blood. EDTA is recommended as providing better organism morphology, particularly for Plasmodium spp. Most patients we see in the US have never been exposed to malaria before, thus they have no antibody. These immunologically naïve patients may present with nonspecific symptoms that can mimic many other diseases. The rule of thumb is to draw immediately. 25

  26. ORGANISM # 15 Modified Acid-Fast Stain: What are the 3 structures shown in the slide (from largest to smallest)? The range is 10 µm to 2 µm. 26

  27. ORGANISM # 16 Iodine wet mount; seen on high dry power, X400 What are morphologic characteristics that help you to identify this structure? 27

  28. ORGANISM # 17 India Ink stain: What and how do you count and how does this help to identify the structure? Name genus, species. 28

  29. ORGANISM # 18 Iodine wet mount: Seen on high dry power, X400. What are structures at each end called? Name genus, species 29

  30. ORGANISM # 19 Iodine wet mount: Identify genus and species – what is structure called in the circle? O 30

  31. ORGANISM # 20 Iodine wet mount: What are the structures within the large object that help you to identify the genus and species? 31

  32. QUESTION 6 What are some of the key report comments associated with malaria reports? What are the pros and cons of the thick and thin blood films? 32

  33. PLASMODIUM SPP. Report Comments • Plasmodium spp. seen: Unable to “rule out” Plasmodium falciparum. • Plasmodium spp. not seen:One negative set of blood films will NOT “rule out” malaria; submit additional blood specimens every 4-6 hours. • Plasmodium spp. seen, possible mixed infection: Unable to “rule out” Plasmodium falciparum. • NOTE: It is mandatory that the parasitemia be calculated and reported for every initial and subsequent positive set of malarial films – the same method for determining parasitemia must be used for all blood film sets on that particular patient. 33

  34. THIN BLOOD FILMS GARCIA 34 • Advantages • RBC morphology can be seen; RBCs preserved • Compare size of infected RBCs to uninfected RBCs • Much easier to identify to species level • Easier to calculate parasitemia (%/100 RBCs) • Disadvantages • Much lower sensitivity than thick blood film • Infections with low parasitemia may be missed

  35. THICK BLOOD FILMS • Advantages • Examining greater volume of blood • May be able to see malaria pigment within WBCs • May be able to see Schüffner's dots • Disadvantages • Can’t compare sizes of infected and uninfected RBCS • Organism distortion is difficult to recognize • Identification to species level is more difficult GARCIA 35

  36. ORGANISM # 21 Cellophane tape: What are these structures and what is the collection method of choice? Name the genus and species 36

  37. ORGANISM # 22 Tissue biopsy, routine H/E stain: What is the cause of this infection? Why might bears, walrus, or pigs be involved? 37

  38. THANKS – QUESTIONS? 38

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