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Analytic Phase of Laboratory Testing

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1 Analytic Phase of Laboratory Testing
Module 4 Analytic Phase of Laboratory Testing

2 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

3 Which test is precise, which test is accurate?
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?

4 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

5 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

6 Automated Medical Laboratory
Photo by – GÜliz A. Barkan, MD

7 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

8 Case Scenario 1 CBC with diff results
WBC 1.0 L [ ] k/ul RBC 2.04 L [ ] m/ul Hgb 7.4 L [ ] gm/dl Hct 22.2 L [ ] % MCV 85 [85-95] fl MCH 28.3 [ ] pg MCHC 33.3 [ ] gm/dl RDW 16.6 H [ ] % Plt Count 7 LL [ ] k/ul Diff Type Manual Blasts % 20 Blasts 0.2 Gran 20 L [45-70] % Gran # 0.2 L [ ] k/mm3 Lymph 45 [20-45] % Lymph # 0.45 [ ] k/mm3 Mono 15 [0-10] % Mono # 0.15 [ ] k/mm3 Eo 0.0 [0-7] % Eo # 0 [ ] k/mm3 Baso 0 [0-2] % Baso # 0.0 [ ] k/mm3

9 Case Scenario 1 Define “manual differential”.
Why was it done in lieu of an “automated differential”?

10 Case Scenario 1 Discussion
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

11 Case Scenario 1 Discussion
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”

12 Case Scenario 1 “flagged” result
Automated CBC report Photos by Theresa Kristopaitis, MD

13 Case Scenario 1 Discussion
The results from the automated count are reviewed by the laboratory technologist A manual slide review is performed

14 Stained Peripheral Blood Smear
Manual Cell Counter Photos by Theresa Kristopaitis, MD

15 differential reported
CBC with manual differential reported Photo by Theresa Kristopaitis,MD

16 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!)

17 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

18 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

19 Proceed to Module 5 “Post Analytic Phase of Laboratory Testing”

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