Diagnostic Techniques Flashcards

1
Q

What is a perfect gold standard of diagnosis?

A

test is 100% specific and sensitive

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2
Q

Is the perfect gold standard of diagnosis often achieved?

A

no

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3
Q

What is a gold standard?

A

best available test: sensitivity & specificity are well defined but less than gold standard

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4
Q

What steps are involved in a direct wet smear?

A
  1. ~2mg feces w/ saline are put on a slide 2. observe under microscope
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5
Q

Why is a direct wet smear not the preferred method of fecal sampling?

A

false negatives bc # of eggs in feces is too low

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6
Q

Describe the formalin-ethyl acetate sedimentation concentration method.

A
  1. mix 4g of feces with formalin 2. strain through gauze 3. mix with saline 4. centrifuge & discard supernatant 5. add more fomalin & ethyl acetate 6. centrifuge & discard supernatant 7. sediment - bottom layer with parasite eggs 8. put small amounts on slide and look under microscope
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7
Q

How are urine samples tested for parasites?

A

sample is collected in clean container -> centrifuge -> examine sediment

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8
Q

How would a blood test be done?

A

sample -> smear -> look under microscope

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9
Q

In which class is Toxocara canis classified?

A

Chromadorea

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10
Q

What is the normal DH of Toxocara canis?

A

dog

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11
Q

How do dogs become infected by Toxocara canis?

A
  1. ingest eggs 2. if pregnant dog becomes infected then larva crosses fetus 3. if lactating dog becomes infected -> transmammary 4. ingest prey with larvae
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12
Q

How does a human become an accidental host in Toxocara canis?

A

ingests eggs

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13
Q

What are visceral larva migrans and ocular larve migrans?

A

visceral larva migrans - larva that migrate through tissues & do not complete development (developmental arrest) just extended random wandering through body vs. ocular larva migrans - inflammation, scarring, blindness

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14
Q

What are the symptoms of Toxocara canis infection?

A

fever, cough, abdominal pain, vision problems

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15
Q

How can an infect be diagnosed and treated?

A

diagnosed by ELISA & treated by mebendazole and albendazole

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16
Q

What is an ELISA?

A

enzyme linked immunosorbant assay

17
Q

Draw and describe the steps involved in this method.

A
  1. serum from patient 2. wash 3. add antibody and enzyme 4. wash 5. add enzyme substrate 6. color change = enzymatic rxn = infection
18
Q

Why are the wash steps necessary?

A

to remove any unbound enzyme

19
Q

What does it mean if there is a color change in the well?

A

infection is present

20
Q

For what types of parasite infections is this diagnostic technique useful?

A

infection where antibody is produced against parasite antigen