Lab Testing.pptx

Perfusion Program OVERVIEW LABORATORY ANALYSIS the use of laboratory tests in clinical practice. • Lab test results interpreted in reference to a population of “similar healthy” individuals • purpose of laboratory testing in different patient populations is to gain normal values • Normal values fo...

Perfusion Program OVERVIEW LABORATORY ANALYSIS the use of laboratory tests in clinical practice. • Lab test results interpreted in reference to a population of “similar healthy” individuals • purpose of laboratory testing in different patient populations is to gain normal values • Normal values for common laboratory tests governs the diagnosis, treatment, and overall management of tested individuals. • Some test results may depend on demographic traits of the tested population like age, race, and sex. Normal Values Personalized or “precision” medicine: match each person to a granular normal reference population. • Precise application of clinical laboratory testing must 1st identify a “healthy” population to estimate the normal range of variation across a population. • Criteria for normality: absence of chronic / acute disease • The Clinical and Laboratory Standards Institute (CLSI) guideline: 120 “Reference individuals” should be used to establish reference intervals for laboratory analytes • Role of Laboratory Testing A. Mass screening: large-scale identification of disease use of tests, examinations, or other procedures which can be applied rapidly. A. Ex COVID, screening the whole family if one had it B. systematic application of a test to identify individuals at sufficient risk of a specific disorder to warrant further investigation B. Diagnosis: ability of a test to identify a disease, condition or injury Clinical diagnosis: diagnosis based on medical signs, symptoms, rather than diagnostic tests. ii. Laboratory diagnosis: diagnosis based on laboratory test results vs physical examination iii. Rule out or rule in disease: the ability of a diagnostic test to lead to the highest (rule in) or lowest (rule out) disease probability and is judged based on likelihood ratios. iii. Confirm diagnosis: A final diagnosis that is made after receiving the results of tests. (blood tests, cath lab (CAD), biopsies etc..) Verify if a certain disease or condition is present. c. Therapy- consists of treatment of disease, control a health problem, lessen its symptoms, cure Ex. CAD tx CABG is lessen the symptoms (pain, QOL inc), CAD, IABP, Stent can still progress – not a cure Principal Functions of Biochemical Tests https://www-clinicalkey-com.proxy.library.emory.edu/#!/content/book/3-s2.0-B9780702079368000028 Specimen Collection completed request should include - properly label • • • • • • • • • patient’s name, sex and date of birth hospital or other patient identification number ward/clinic/OR name of requesting doctor clinical diagnosis/problem test(s) requested type of specimen date and time of sampling relevant treatment (e.g. drugs) not likely for OR) Specimen Collection Serum- whole blood goes into a red topped tube with no reagent to affect clotting factors, blood is spun in a centrifuge. • Heavy components sink to the bottom of tube (RBC, plat, clots), while light components migrate to the top (WBC). Fluid at the top is pipetted off (serum – clotted off in red top tube, not prevented by reagent, there are no active clotting factors) Plasma- whole blood is goes into a purple topped tube which contains a reagent Ethylenediaminetetraacetic acid (EDTA)-EDTA: EDTA: A chemical that binds certain metal ions, such as calcium, magnesium, lead, and iron (prevents clots) • Iused prevent blood samples from clotting • Blood is spun in a centrifuge. Heavy components to the bottom of tube, while light components are on the top. • Fluid at the top is pipetted off (plasma – clotting factors are active, reagent EDTA doesn’t allow clotting factors to be used up) Specimen Collection Hemoglobin in RBC Hemolysis: rupture or destruction of red blood cells • Hemolysis is a natural process where the body destroys older RBCs (120 days) that no longer work efficiently. Thru spleen and lysis if old. – Some conditions, medications, and toxins break down RBC early Hemolysis causes* Causes extrinsic, outside source. intrinsic, from the RBC itself, causes own destruction. Extrinsic certain conditions / outside factors that destroy RBC, such as: chemicals infections Medicines: penicillin, acetaminophen, and clopidogrel increased spleen activity immune reactions: incompatible blood transfusion mechanical damage: artificial heart valves (vs bio wont hemolyze as much), hemodialysis and heart-lung bypass machines (over occlusion, or long case, sucker, vent) (bloody urine) • Toxins: lead and copper • Poisons: venoms • • • • • • • • • • Hemolysis causes* •Intrinsic •conditions changes within the RBC itself cause hemolysis. •deformities in structure, metabolism or hemoglobin structure. •These conditions may include: •hereditary cell membrane conditions: hereditary spherocytosis •Hemoglobinopathies: thalassemia, sickle cell disease •conditions affecting RBC metabolism: glucose-6-phosphate dehydrogenase deficiency •abnormalities in the RBC membrane (structure): elliptocytosis Specimen Collection CASE HISTORY The laboratory system flagged up a blood result on a request generated from the diabetes clinic for a pre-appointment check, with the following results: Serum: sodium 140 mmol/L potassium 12.2 mmol/L (^) creatinine 84 μmol/L (^) calcium 0.34 mmol/L (low) phosphate 1.22 mmol/L (^) High: potassium, Hemolyzed sample ?? Specimen Collection Chart to know * Sample Analysis and Reporting of Results lab definitions * analytical method is accurate, precise, sensitive and specific • Accuracy: test method gives results that are correct (compared “gold standard” ) true results • Precision: result method gives the same result if repeated (same result each time) • Analytical Sensitivity: (LAB) test able to measure low concentrations of the analyte – Lab run, high sensitivity troponin test: low concentrations of trops measured • Analytical Specificity: (LAB) test is not subject to interference by other substances – Drugs could interfere, low specificity if so Note: different than statistical terms of sensitivity and specificity • test should be cheap, simple and quick. • practice no test is ideal, but laboratory staff make considerable efforts to ensure that the results are sufficiently reliable to used. Analytical methods are subject to rigorous quality-control and quality-assurance procedures. Precision vs. Accuracy Sources of Error* Error: Erroneous results have potential for causing harm and can occur at various: • preanalytical: outside the laboratory (incorrect specimen being collected, mislabeling, incorrect tube, incorrect patient sticker, time to get to the lab, vacuum system) • analytical: in the laboratory (human training/new or instrument error) • postanalytical, correct result generated, incorrectly recorded or misinterpreted. Analytical errors a. systematic (bias): different analytical methods may produce results higher or lower than the definitive or reference method b. random: no set pattern Clinical Specificity and Sensitivity* • specificity of a test is a measure of the incidence of negative results in persons who don’t have the disease. [true negative (TN)] – negative no SC • Sensitivity is a measure of the incidence of positive results in patients known to have the disease. [true positive (TP)]. – positive for SC • A false positive (FP) something is true when it is false (also called a type I error). A false positive is a “false alarm.” – positive but no SC • A false negative (FN) something is false when it is actually true (also called a type II error). Clinical Specificity and Sensitivity Laboratory Terminology POCC – Point of Care Coordinator  Manages all of duties for instrument compliance with regulations Medical Director – Usually the Laboratory Director; the individual named on the CMS/CLIA license; has final responsibility for all testing at site certification. The Centers for Medicare & Medicaid Services (CMS) Clinical Laboratory Improvement Amendments (CLIA) regulates the quality and safety of U.S. clinical laboratories to ensure the accuracy, reliability, and timeliness of patient test results regardless of where the test was performed. Reference Interval – new term meaning Normal Range Proficiency Testing:  Samples of unknown values sent to subscribing sites 2-3 x’s annually to evaluate the site’s performance against the central laboratory  Allowable failure is 20% or 1 in 5 challenges Laboratory Terminology EQC – Electronic Quality Control  Method for verifying all internal components are functioning within specifications  Can be entirely internal (ABG lab tester) LQC -Liquid Quality Control (glucometer)  Emulates  Always a patient sample w/material of known values a liquid  Different manufacturers have own methods for preparing For Compliance  Laboratory license  Validation prior to patient testing  Policies and Procedures  Training and competency  Calibration and calibration verification  Result reporting  Proficiency testing  Record retention  Reagent management  Quality management  Complaint and issue follow-up Validation  Required: minimum of 10 of each level of LQC; (LQC -Liquid Quality Control (glucometer) performed over several days to account for minor environmental changes and operators  every instrument  Use of fully validated instrument for Reference Interval and Method Correlation  Pump: in line electro/ABG measurement, accurate till compared to ABG collected for lab and calibrate (SvO2 for a SWAN) Training and Proficiency  Required: every operator must be documented as participating in: Initial training Re-Training Annual training thereafter  Operators events at 6-month post implementation must participate in Proficiency Testing Calibration The process of adjusting the output delivered by the measurement device to align with the value of the applied standard of known accuracy. Point of Care Testing Devises POCT: any tests that’s performed at or near a patient where care / treatment is provided. •Results typically available quickly so that they can be acted upon without delay ** Point of Care Testing       Performed on whole blood Less expensive Must meet same quality control standards as the central Lab Results returned quickly – 2 to 10 minutes Types: activated clotting time / plasma heparin concentration / PT or aPTT Thromboelastography / sonoclot (whole blood to clot) Why Use POCT Devices Improved Clinical Outcomes  Reduces OR time  Reduces bleeding  Reduced blood TX Reduced LOS  Improved, timely patient care  POCT limitations Blood Gas balanced heparinized syringes or clots will develop, inaccurate electrolyte results may occur Air bubbles inaccurate blood gas results Failure to mix will cause clots, falsely low hemoglobin Ionized calcium results different from Total calcium by laboratory Potassium can be falsely elevated by masked hemolysis Unlabeled syringes may result results going to wrong patient caregivers POCT limitations Glucometers/ketone meters • unreliable if peripheral circulation is impaired and can over/underestimations true glycemic status. ex: • Severe Dehydration due to Diabetic Ketoacidosis • Hypotension • Shock • Decompensated heart failure NHYA Class IV • If peripheral circulation is impaired send a sample to the laboratory or use a venous sample better for glu than ABG • Only heparinized samples can be used – other anticoagulants wrong • Continued glycolysis will adversely effect results if not analyzed immediately • Any sample glucose reading below 2.8 mmol/L or above 20 mmol/L, or which is not in keeping with the clinical picture, should be verified by sending a venous specimen of blood to the laboratory. – suspect lol Will POC Testing Results Match the Lab Match (Probably Not but they should Correlate Characterist ics of POCT Devices POINT-OF CARE ANALYZERS ABL 77 i‐ STA T Gem Premier 3000 Stat Profile AVL Omni C IRMA TruPoint RapidPoint 500 IN-LINE BLOOD GAS ANALYZERS CDI System 500 Spectrum Medical Medtronic HMS Heparin Management System Medtronic HMS Heparin Management System • Help prevent thrombus formation and preserve clotting factors • Monitor multiple parts anticoagulation The HMS Plus technology was created with the recognition that (ACT) is a global or functional test that measures the effect of: • Medications • Heparin anticoagulation • Temperature • Dilution Measuring the ACT (degree of anticoagulation) doesn’t always mean adequate heparinization or if appropriate antithrombotic state occured. Hemostasis management is achieved with the HMS Plus System for OR, ECMO, and when Pointof-Care heparin testing is important to successful medical treatment. Medtronic HMS Heparin Management System Optimized patient treatment using the HMS Plus System includes: Test Cartridges Used Measuring actual circulating heparin concentration Heparin Assay Cartridges Assessing patient’s individual response to heparin Heparin Dose Response (HDR) ACT tests High Range ACT (HR-ACT) Medtronic HMS  Dose response cartridge – candy cane (red/white) ◦six wells ◦1 & 2: 2.5 u/ml heparin ◦3 & 4: 1.5 u/ml heparin ◦5 & 6: no heparin  Makes dose response curve - predicts loading dose of heparin ◦Need to add in patient height, weight and pump prime volume HEPARIN DOSE RESPON SE (HDR) • Project individual responses to heparin • Determines appropriate heparin dose for each patient • achieve target act (480s) • Identifies resistant or sensitive patients • Minimizes heparin over and under dosing Medtronic HMS HEPARIN/PROTAMINE TITRATION • Each channel contains a different concentration of protamine • channel that neutralizes the heparin in the sample will be the first to clot. • tell how much heparin to give to get back to target ACT (480) or how much protamine to neutralize heparin. HMS HEPARIN/PROTAMINE TITRATION HMS System functions • Quantitative test that determines actual heparin concentration • Measures the heparin concentration by identifying the known amount of protamine concentration that optimally neutralizes heparin • Allows maintenance of desired heparin level • Calculates protamine reversal dosage ADDITIONAL POINT OF CARE DEVICES THAT MEASURE COAGULATION Thromboelastography (TEG) • ROTEM • Sonoclot Thromboelastography (TEG) Thromboelastography (TEG) is a viscoelastic hemostatic assay measures the global viscoelastic properties of whole blood clot formation under low shear stress TEG shows the interaction of platelets and. coagulation cascade (aggregation, clot strengthening, fibrin cross-linking and fibrinolysis) does not necessarily correlate with blood tests such as INR, APTT and platelet count (which are often poorer predictors of bleeding and thrombosis) This page describes TEG® predominantly, ROTEM® is the alternative viscoelastic hemostatic assay that is widely available commercially TEG Method & Subtests • Whole blood placed in a citrated tube (no reagent), then transferred to a tube containing kaolin (activator) • TEG® measures physical properties of the clot in whole blood with pin suspended in a cup (heated to 37C) from a torsion wire connected with a mechanical-electrical transducer • elasticity / strength of developing clot, causes change in rotation of the pin • change is converted into electrical signals that a computer uses to create graphical and numerical output point • Conventional TEGNATEM (TEG® using native whole blood) is slower, takes around 30min • RapidTEG®: Kaolin and kaolin + tissue factor (TF) () are used as activators, relatively quick a. Tissue factor triggers extrinsic pathway, has smaller number of coagulation factors, test is faster than conventional TEG. b. Rapid TEG can be completed within 15 minutes and thus helps manage massive transfusions in trauma patients. • Functional fibrinogen: measures of fibrin-based clot function • Platelet Mapping: whole blood is collected and placed in a lithium heparin tube then placed in a Kaolin with Heparinase tube. a. evaluates platelet function by evaluating the receptors on platelets TEG6s (Haemonetics) •newer machine doesn’t use ‘pin-in-cup’ technique (like TEG5000 predecessor) •uses ‘resonance’ blood is exposed to a fixed vibration frequency range and the detector measures the vertical motion of blood meniscus under LED illumination and transforms that movement into tracing of clot dynamics •Uses pre-prepared cartridges, not pipetting •CUP IS MOVING!! TEG Variables ** KNOW •R value = reaction time (s) • time of latency from start of test to initial fibrin formation (amplitude of 2mm) • initiation phase • dependent on clotting factors •K = kinetics (s) movement, time it takes • time taken to achieve a certain level of clot strength (amplitude of 20mm) • amplification phase • dependent on fibrinogen •alpha = angle (slope of line between R and K) • measures the speed at which fibrin build up and crosslinking takes place, hence assesses the rate of clot formation • “thrombin burst” / propagation phase • dependent on fibrinogen •TMA = time to maximum amplitude(s) •MA = maximum amplitude (mm) • represents the ultimate strength of the fibrin clot; i.e. overall stability of the clot • dependent on platelets (80%) and fibrin (20%) interacting via GPIIb/IIIa •A30 or LY30 = amplitude at 30 minutes • percentage decrease in amplitude at 30 minutes postMA • fibrinolysis phase •CLT = clot lysis time (s) TEG Normal Values * •Approximate normal values (kaolin activated TEG, values differ if native blood used, and between types of assay) •R: 4-8 min •K: 1-4 min •α-Angle: 47-74° •MA: 55-73mm •LY 30%: 0-8% TEG AND ROTEM TRACING TEG AS A GUIDE TO TREATMENT Increased R time => FFP Decreased alpha angle => cryoprecipitate Decreased MA => platelets (consider DDAVP) Fibrinolysis => tranexamic acid (or aprotinin or aminocaproic acid) TEG Qualitative Analysis ** TEG® VERSUS ROTEM® viscoelastic tests: • Thromboelastography =TEG® (produced in the USA) move cup • Rotational thromboelastogram = ROTEM® (Germany) move pen • Differences in diagnostic nomenclature for identical parameters between the two • TEG® operates by moving a cup in a limited arc (±4°45′ every 5s) filled with sample that engages a pin/wire transduction system as clot formation occur • ROTEM® has an immobile cup wherein the pin/wire transduction system slowly oscillates (±4°45′every 6s) • results not directly comparable, different coagulation activators used • ROTEM® is more resistant to mechanical shock, which may be an advantage in the clinical setting TEG® VERSUS ROTEM® Equivalent variables for ROTEM® •Clotting time (CT) = R value (reaction time) •α angle and clot formation time (CFT) = K value and α angle •Maximum clot firmness (MCF) = Maximum amplitude (MA) •Clot lysis (CL) = LY30 ROTEM TEG Clotting time (CT) R value (reaction time) α angle and clot formation time (CFT) K value and α angle Maximum clot firmness (MCF) Maximum amplitude (MA) Clot lysis (CL) LY30 Platelets & Platelet Aggregation * Subendothelial macromolecules such as von Willebrand factor and collagen interact with glycoprotein receptors (GPVI and GPIb) on platelets, causing activation of platelets and upregulation of GPIIb/IIIa receptors, which are crosslinked by fibrinogen, resulting in aggregation. During the initial processes of aggregation, stimulation of the synthesis and release of several platelet-derived substances, such as adenosine diphosphate (ADP), thromboxane A2 (TXA2), which is synthesized from arachidonic acid (AA) by cyclo-oxygenase-1 (COX-1), and other factors (described previously) further promote aggregation by upregulation of GPIIb/IIIa receptors. Conversely, prostacyclin (PGI2) from endothelial cells inhibits the activation and upregulation of GPIIb/IIIa receptors.. Mechanism of Action of Antiplatelets Sites for Major Antiplatelet Drugs. Drugs act directly or indirectly to block activation of platelets and inhibit upregulation of the glycoprotein GPIIb/IIIa receptors (integrin receptor family), which are necessary for platelet aggregation. Abciximab is an antibody, tirofiban a nonpeptide inhibitor and eptifibatide a peptide inhibitor of these glycoprotein receptors. Clopidogrel and related drugs inhibit ADP (P2Y12) receptors and prevent ADP-induced upregulation of the glycoprotein GPIIb/IIIa receptors. Aspirin inhibits the generation of thromboxane A2 (TXA2) by cyclooxygenase-1 (COX-1), which otherwise causes platelet activation and upregulation of GPIIb/IIIa receptors. AA, ADP, SONOCLOT COAGULATION & PLATELET FUNCTION ANALYZER Platelet Mapping The Sonoclot Analyzer: measure coagulation and platelet function in whole blood or plasma. • manages anticoagulant therapy, assess platelet function, control blood product usage, differentiate mechanical versus hemostatic bleeders, identify hypercoagulable and heparin resistant patients, and screen for hyperfibrinolysis. • Clinical areas include open heart surgery, liver transplant surgery, vascular surgery, orthopedic surgery, obstetrics/neonate care, cardiology, trauma and hemostasis research. • Uses whole blood viscoelastic clot detection mechanism. • Provides accurate information on the entire hemostasis process including coagulation, fibrin gel formation, clot retraction (platelet function), and fibrinolysis. • Generates both a qualitative graph, known as the Sonoclot Signature, and quantitative results on the clot formation time a. (Activated Clotting Time - Onset) b. the rate of fibrin polymerization (Clot RATE). c. The Onset and Clot RATE results are automatically calculated and appear on the LED display and are printed on the hard copy graphic output. Platelet Mapping • Thromboelastography with platelet mapping (TEG-PM) measure platelet function (antiplat meds) • two components: a. Arachidonic acid (AA), sensitive to aspirin (nonsteroidal antiinflammatory drugs (NSAIDs) b. Adenosine diphosphate (ADP), sensitive to clopidogrel. Platelet Functio n Testing Platelet aggregometry is the gold standard test for diagnosing platelet function disorders. It is generally the preferred test when a platelet function disorder is suspected. Specialized The VerifyNow test is a type of whole blood aggregometry that has been automated Platelet Aggregometry Platelet aggregometry: a series of tests performed on whole blood or platelet-rich plasma, using several agonists (platelet activators) to activate specific pathways associated with platelet aggregation. • The agonist is added to the suspension and a measurement of platelet clumping is recorded. • Changes of optical density are plotted to view the aggregation curve. Platelet Aggregometry •The VerifyNow test is a type of whole blood aggregometry that has been automated. Platelet Aggregometry https://youtu.be/zk7Qg5s6nLc