Module 4
Analytic Phase of
Laboratory Testing
Analytical Phase
O 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
O Current methods and equipment used to
generate test results have a high degree of
O Accuracy
=Correctness – how closely the measurement
approaches the true value of the substance being
analyzed (analyte)
O Precision
=Reproducibility – how closely together are results from
measurements of the same substance in the same
sample
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?
Precision, Accuracy or Both?
O Years ago, it was often said that precision
was more important than accuracy in lab
testing
O Why?
O 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
O Presently, most common laboratory tests are
both accurate and precise
Automation
O Many laboratory tests are performed on
automated instruments.
O Automation and information technology are widely
used to minimize the degree to which manual
techniques need to be employed in many testing
situations
O There are a number reasons for this trend
including:
O Advances in technology
O The continuing shortage of allied healthcare
personnel entering the field of laboratory
medicine
Automated Medical Laboratory
Photo by – GÜliz A. Barkan, MD
Case Scenario 1
O A 32-year old man presents with a 3 week
history of fatigue. On physical exam he
appears pale and has scattered petechiae.
O His physician begins a diagnostic evaluation:
he orders, among other tests, a CBC with
differential
Case Scenario 1
CBC with diff results
WBC
RBC
Hgb
Hct
MCV
MCH
MCHC
RDW
Plt Count
Diff Type Manual
Blasts %
Blasts
Gran
Gran #
Lymph
Lymph #
Mono
Mono #
Eo
Eo #
Baso
Baso #
1.0
L
2.04 L
7.4
L
22.2 L
85
28.3
33.3
16.6 H
7
LL
[4.0-10.0] k/ul
[3.60-5.50] m/ul
[12.0-16.0] gm/dl
[34.0-51.0] %
[85-95] fl
[28.0-32.0] pg
[32.0-36.0] gm/dl
[11.0-15.0] %
[150-400] k/ul
20
0.2
20 L
0.2 L
45
0.45
15
0.15
0.0
0
0
0.0
[45-70] %
[2.0-7.0] k/mm3
[20-45] %
[1.0-4.0] k/mm3
[0-10] %
[0.0-1.0] k/mm3
[0-7] %
[0.0-0.7] k/mm3
[0-2] %
[0.0-0.2] k/mm3
Case Scenario 1
O Define “manual differential”.
O Why was it done in lieu of an “automated
differential”?
Case Scenario 1
Discussion
O 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
Case Scenario 1
Discussion
O Data generated by the instrument that are
not acceptable based on defined criteria are
“flagged” to alert the technologist that
further investigation is required
O In this case the marked leukopenia,
thrombocytopenia and anemia resulted in the
“flag”
Case Scenario 1
“flagged” result
Automated CBC report
Photos by Theresa Kristopaitis, MD
Case Scenario 1
Discussion
O The results from the automated count are
reviewed by the laboratory technologist
O A manual slide review is performed
Stained Peripheral Blood Smear
Manual Cell Counter
Photos by Theresa Kristopaitis, MD
CBC with manual
differential reported
Photo by
Theresa Kristopaitis,MD
Despite Advances in Automated Laboratory
Techniques…
O Some laboratory tests are still performed
manually or have manual components
O Hematology (as the case illustrated),
microbiology and fluid labs employ medical
laboratory technologists who are well-trained in
microscopic analyses
O In addition, staff techniques in pipetting,
vortexing or staining may affect lab results
(remember your days in chemistry lab!)
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
Lab Testing is Highly
Regulated
O It is critical that clinical laboratory staff adhere
to:
O A multitude of rigorous accreditation and regulatory
requirements such as:
O
O
O
O
O
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
O Proceed to Module 5 “Post Analytic Phase of
Laboratory Testing”