Module 4 Analytic Phase of Laboratory Testing Analytical

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 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 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 MCHC RDW Plt Count Diff Type Manual Blasts % Blasts Gran # Lymph # Mono # Eo Eo # Baso # 1. 0 2. 04 7. 4 22. 2 85 28. 3 33. 3 16. 6 7 L L H LL 20 0. 2 20 L 0. 2 L 45 0. 45 15 0. 0 [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 [45 -70] % [2. 0 -7. 0] k/mm 3 [20 -45] % [1. 0 -4. 0] k/mm 3 [0 -10] % [0. 0 -1. 0] k/mm 3 [0 -7] % [0. 0 -0. 7] k/mm 3 [0 -2] % [0. 0 -0. 2] k/mm 3

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 Use of standard operating procedures O Appropriate performance of quality control measurements O Instrument calibration schedules O Instrument preventative maintenance schedules O 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”