Clinical Specimen Basics I and II Flashcards Preview

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Flashcards in Clinical Specimen Basics I and II Deck (30)
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describe the flow of patient's symptoms --> lab --> potential treatment


describe a direct method

culture (look for/detect the agent)

  • advantages
    • allows anti-microbial susceptibility testing
    • allows typing of the microorganism
    • allows storage of the strain
  • disadvantages
    • depends upon the viability/condition of the agent
    • turn around time is long


describe direct blotting vs. PCR

  • direct blotting:
    • no amplification (enough DNA)
      • DNA of the agent is released
        • gets spotted onto a membrane and fixed
        • is recognized by labeled probes (hybridization)
  • PCR
    • amplification (not enough DNA)
    • rapid, high sensitivity and specificity
    • use in most virology testing


describe Ag/Ab testing (indirect method)

detects host response to the agent

  • advantages
    • inexpensive
    • easy to perform
    • allows identification of
      • IgM (acute infxn)
      • IgG (past infxn)
  • disadvantages
    • delayed response
      • false negative results during sero-conversion window
    • time of infection not always clear


describe immuno-diagnosis of acute infections

  • draw an acute serum
    • within 7-14 days
      • titers are usually zero or low at <7 days
  • draw a convalescent serum 3-6 weeks after the first serum
    • look for a 4 fold or greater titer increase due to IgG
      • if initial titer is 1:4, the convalescent titer should be 1:16 or greater


describe testing for congenital infections

check antibody titer for agents suspected (CMV, Toxoplasma, etc.)

  • test at birth (cord blood serum)
  • test baby again after 3-4 months
  • if baby is negative for infection:
    • IgM should NOT be present
    • IgG titer from mother will drop at rate of 50% loss every month and will never go back up
      • in 3 or 4 months, the baby titers are low or negative
  • baby positive for infection:
    • IgM will be positive and IgG titers eventually go up


describe interpreting a single, acute IgM test


describe interpreting a single, acute IgG test


what can you do if you miss the acute titer?

  • draw a convalescent titer when titer is high
    • 3-6 weeks after the start of the infection
  • a very high convalescent titer, and if the clinical symptoms agree, the infection can be presumptively confirmed
    • a single positive antibody usually does not allow a definitive confirmation of most acute infxns
    • exceptions are the chronic infxns:
      • lyme disease
      • HIV infxn
      • hepatitis infxns


describe diagnosis of HIV

  • do assays to check for presence of a variety of antibody types to increase test specificity
    • tests for a panel of antibodies to surface and internal proteins helps eliminate false positive reactions due to just one or two cross-reacting common antigens between closely related microbes
    • a Western blot procedure is one way to produce a variety of separate antigens from the virus or bacterium of interest so that these antigens can be used to test for distinct antibodies from the patient
    • PCR for nucleic acid


describe throat swabs (sampling technique)

  • hold tongue away with tongue depressor
  • locate areas of inflammation and exudate in posterior pharynx, tonsillar region of throat behind uvula
  • avoid swabbing soft palate; do not touch tongue
  • rub area back and forth with cotton or Dacron swab


describe nasopharyngeal swab (sampling technique)

  • tilt head backwards
  • insert flexible fine-shafted polyester swab into nostril and back to nasopharynx
  • leave in place a few seconds
  • withdraw slowly; rotating motion


describe sputum (sampling technique)

  • instruct patient to take a deep breath and cough up sputum directly in a wide-mouth sterile container
    • avoid saliva or postnasal discharge
    • 1 ml minimum volume


describe a good sputum sample


describe urine sampling

  • midstream: clean-catch technique
    • clean periurethral area with soap and water
    • pass initial urine into toilet and then collect
    • for: urine culture and other rapid tests
  • first catch specimen:
    • clean area
    • urine for chlamydia and gonorrhea testing


describe sampling catheterized urine

  • clean periurethral area with soap and water
  • insert catheter into bladder
    • discard initial urine
    • collect specimen in sterile cup
  • chronic indwelling Foley catheter
    • clamp tubing below junction (or port)
    • disinfect with alcohol
    • insert needle (or syringe) through port or catheter wall and aspirate 


describe suprapubic aspiration

  • be certain bladder is full--palpate or percuss
  • prep skin with alcohol or iodine
  • anesthetize with lidocaine
  • introduce needle 2.0 cm above symphysis
  • aspirate 20 ml for culture


describe a good urine sample


describe a bad urine sample


do not refrigerate ___ samples 

do not refrigerate STD samples 

e.g. Neisseria gonorrhea


describe sampling a wound specimen


describe anaerobic bacterial cultures


describe blood cultures


describe disinfection of site and recommendations for blood cultures


describe a good blood sample


you need at least ___ identifiers for labeling specimens

you need at least identifiers for labeling specimens

  • patient's name
  • unique ID number
  • specimen type
  • data, time and place of collection
  • name/initials of collector


describe transport media


describe transport media for anaerobic bacteria and viruses


describe ova and parasite exam and transport


describe storage of specimens