Module%204

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Module 4

• Analytic Phase of Laboratory Testing

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Analytical Phase

• It may be surprising, but current technology has
  resulted in the analytical phase now having the
  least error of the 3 phases of laboratory testing
• Current methods and equipment used to generate
  test results have a high degree of
• Accuracy
• Correctness how closely the measurement
  approaches the true value of the substance being
  analyzed (analyte)
• Precision
• Reproducibility how closely together are
  results from measurements of the same substance
  in the same sample

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Test is neither precise nor accurate
Test is precise but not accurate
Test is precise and accurate
Which test is precise, which test is accurate?
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Precision, Accuracy or Both?

• Years ago, it was often said that precision was
  more important than accuracy in lab testing
• Why?
• A lab test which is precise but not accurate may
  still be clinically useful if the data is used to
  follow trends or if the lab has properly set its
  own reference or normal range
• Presently, most common laboratory tests are both
  accurate and precise

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Automation

• Many laboratory tests are performed on automated
  instruments.
• Automation and information technology are widely
  used to minimize the degree to which manual
  techniques need to be employed in many testing
  situations
• There are a number reasons for this trend
  including
• Advances in technology
• The continuing shortage of allied healthcare
  personnel entering the field of laboratory
  medicine

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Automated Medical Laboratory Photo by GÜliz A.
Barkan, MD
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Case Scenario 1

• A 32-year old man presents with a 3 week history
  of fatigue. On physical exam he appears pale and
  has scattered petechiae.
• His physician begins a diagnostic evaluation he
  orders, among other tests, a CBC with
  differential

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Case Scenario 1CBC with diff results

• WBC 1.0 L 4.0-10.0 k/ul
• RBC 2.04 L 3.60-5.50 m/ul
• Hgb 7.4 L 12.0-16.0 gm/dl
• Hct 22.2 L 34.0-51.0
• MCV 85 85-95 fl
• MCH 28.3 28.0-32.0 pg
• MCHC 33.3 32.0-36.0 gm/dl
• RDW 16.6 H 11.0-15.0
• Plt Count 7 LL 150-400 k/ul
• Diff Type Manual
• Blasts 20
• Blasts 0.2
• Gran 20 L 45-70
• Gran 0.2 L 2.0-7.0 k/mm3
• Lymph 45 20-45
• Lymph 0.45 1.0-4.0 k/mm3
• Mono 15 0-10
• Mono 0.15 0.0-1.0 k/mm3
• Eo 0.0 0-7

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Case Scenario 1

• Define manual differential.
• Why was it done in lieu of an automated
  differential?

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Case Scenario 1Discussion

• Initial specimen analysis was performed by the
  automated instrument

Recall the color of the collection tube caps
for a CBC?
Photo by Theresa Kristopaitis, MD
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Case Scenario 1Discussion

• Data generated by the instrument that are not
  acceptable based on defined criteria are
  flagged to alert the technologist that further
  investigation is required
• In this case the marked leukopenia,
  thrombocytopenia and anemia resulted in the
  flag

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Case Scenario 1flagged result
Automated CBC report
Photos by Theresa Kristopaitis, MD
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Case Scenario 1Discussion

• The results from the automated count are reviewed
  by the laboratory technologist
• A manual slide review is performed

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Stained Peripheral Blood Smear
Manual Cell Counter
Photos by Theresa Kristopaitis, MD
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CBC with manual differential reported
Photo by Theresa Kristopaitis,MD
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Despite Advances in Automated Laboratory
Techniques

• Some laboratory tests are still performed
  manually or have manual components
• Hematology (as the case illustrated),
  microbiology and fluid labs employ medical
  laboratory technologists who are well-trained in
  microscopic analyses
• In addition, staff techniques in pipetting,
  vortexing or staining may affect lab results
  (remember your days in chemistry lab!)

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Gram stain reagents used by Microbiology Lab
Technologists to prepare smears
Gram stain of a positive blood culture What is
your interpretation?
Gram Positive Cocci in Clusters
Photos by Theresa Kristopaitis, MD
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Lab Testing is Highly Regulated

• It is critical that clinical laboratory staff
  adhere to
• A multitude of rigorous accreditation and
  regulatory requirements such as
• Use of standard operating procedures
• Appropriate performance of quality control
  measurements
• Instrument calibration schedules
• Instrument preventative maintenance schedules
• Participation in external reviews of analyte
  testing (proficiency testing)
• These measures help ensure the quality of the
  process during the analytical phase of patient
  testing

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• Proceed to Module 5 Post Analytic Phase of
  Laboratory Testing