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Procedure of Laboratory Test and Factors Affecting Reliability of Test Result
Usi Sukorini Departement of Clinical Pathology Faculty of Medicine UGM 2012
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input process output
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Effects of Variables on the Quality of Laboratory Testing
Para-analytical variables (pre & post analytical variables) Analytical variables Pre Analytic Post Test requests/ordering Patient identification Specimen acquisition Specimen transport Specimen processing Preparation of worklists and logs Maintenance records Result reporting Result interpretation Result distribution Competency Controls Methodology Procedures Monitoring of equipment Monitoring of materials Test validation
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Process of laboratory test request
Order test Collect sample Transport sample to lab Receive sample in lab Prepare samples for testing Transport sample to lab section Results Verifications Send to clinicians
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PREANALYTICAL PHASE
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Expanded View of the Preanalytical Phase
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Preanalytical phase The processes prior to the actual analysis of the sample Include steps needed to obtain the primary sample (e.g. blood) and to obtain the analytical specimen (e.g. plasma, serum, cells) KNOWLEDGE Preparation Primary sample Analytical specimen
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Impact of Preanalytic Phase on Laboratory Test Outcomes
Preanalytic Steps are Labor Intensive Steps in specimen collection are many and varied Potential for error expands as the number of steps increase Studies state that “32 to 75%” of inaccurate test results originate from the preanalytic phase
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Ordering tests Order Test: Appropriate indication
Complete & correct order Deploy staff for collection Note urgency level Collect supplies
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Ordering test Indications: Indications: Screening Diagnosis
Confirmation Therapy Monitoring Indications: Sex Age Time of collection Type of specimen Urgency
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Methods of test Performance of test Analytic Diagnostic
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Patient Preparation Fasting: Postprandial
Glucose, cholesterol: hours prior venipuncture Postprandial At specific time in a hormonal cycle: Cortisol and adrenocorticotropin, have diurnal variations, where the analyte is at its highest level in the morning, and the levels gradually decrease during the course of the day Before or After Medication Dosage Upon Rising or after being awake for a specific period of time
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Patient identification
Full name, address, identification number and/or date of birth Sex Other information in request form: Doctor’s name & contact number Clinical manifestation Treatment Time of blood collecting
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Specimen collection Prolonged tourniquet time can lead to an increase in various chemistry analytes, including serum protein, potassium and lactic acid due to hemoconcentration of blood at the puncture site Prolonged tourniquet application with leak of interstitial fluid into tissue Correct phlebotomy technique Complete fill of tubes
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Specimen collection Incomplete alcohol drying following site preparation Shear stress and subsequent rupture of red cells when collected with small bore needle Tissue trauma during collection Slow blood flow Occlusion of needle lumen by vein wall
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Specimen collection Blood Collection from Indwelling Lines
Collection by Alternate Healthcare Providers Education is Key for Healthcare Team Specimen Quality Issues Hemolysis Fluid Contamination Dilution of Samples
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Collecting the right specimen is of critical importance, for example:
if a diagnosis of meningitis is expected, obtaining a throat swab or a sputum sample (instead of CSF) would not be the best sample for this purpose Coagulation test: citrated plasma IgG anti dengue: should be collected > 5 days of fever
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Labelling Label All Samples at the Bedside
Handwritten Labels Must be Legible All Labels Must Contain Required Information Attached Labels Should Follow Guidelines for Optimum Usefulness
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Prolonged transportation and storage
Prolonged and improper storage prior to processing of the specimen can affect the results especially since many organisms do not survive for long unless they are subcultured or kept in an environment which is rapidly changing, or vice versa Over 0r understimation of test result Platelet count PT, APTT
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Age-dependent variations
Age dependent changes of concentration or activities occur in a number of haematological and chemical analytes Normal bacteriological flora also change with age. Hence laboratory results should be interpreted keeping in view the age of the patient
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Variable Analyte Levels
Potassium, LDH, Mg, iron Increased by Hemolysis Glucose When Cells and Serum are Not Promptly Separated
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Effects of Improper Inversion
Clotted Samples Improper Mixing of Anticoagulant with Collected Blood Clotting Process Utilizes Clotting Factors Clotted Samples Can Not Be Analyzed in Instrumentation Require Re-Collection
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Avoid The “Excessives”
Do NOT SHAKE Causes Hemolysis Avoid Excessive Heat or Cold Deterioration of Analytes Never Expose Whole Blood to Dry Ice Freezing Causes Hemolysis
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Transportation Transport All Samples to the Laboratory as Efficiently as Possible Transport To Lab: Prioritize sample for transport Send sample to lab Pneumatic tube Robot Hand carry Courier
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Causes of hemolysis The presence of hemolysis in the serum or plasma of a sample appears as a pink or red color to the liquid after centrifugation (or separation from blood cells)
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Vigorous shaking of collection tubes
Frothing (buih/gelembung)of blood resulting from a loose connection of the blood collection assemblies when performing line draws Freezing of red blood cells during storage or transportation Exposure of cells to excessive heat during storage or transportation Prolonged contact of serum or plasma with cells
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Impact of Preanalytical Errors
Unusable Samples due to Quality Issues Specimen Rejection Specimen Recollection Compromise of Quality Analysis Delay or Inaccuracy in Diagnosis and Treatment Possible Compromise of Patient Safety
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Suggested indicators for the preanalytical phase
Standard operating procedures for specimen acceptance /rejection to be followed by all staff Identification and monitoring of reasons for specimen rejection Effect of improvement initiative in decreasing the rate of specimen rejection Comparison between clinical laboratories (bench marking) of frequency and reasons for specimen rejection
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Suggested indicators for the preanalytical phase
Potential performance measures for pre-analytical phase Indicators of patient identification - Wrong patient ID on the sample - Missing patient ID on the sample - Illegible patient ID on the sample (tidak dapat dibaca) - Request unintelligible Indicators of Sample collection - Wrong collection time - Inadequate/ inappropriate container - Inadequate volume, Inappropriate volume to anticoagulant ratio - Contaminated from IV line
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Suggested indicators for the preanalytical phase
Indicators for sample transport - Storage condition (temperature, high exposure) - Sample deliver to the lab outside specified time - Sample lost or not received in the laboratory General indicators - Physician complains - Sample recollection - Sample retesting - Correction of ordered test - Results delivery to the physician outside specified time
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.. The pre-analytical stage is the most important and can be critical to patient wellbeing The analytical stage and post analytical stages depend primarily on the Quality and Integrity of the specimen submitted to the laboratory (Pre-Analytical) Laboratory staff involved in specimen collection have a direct impact on the outcome of patients lab results
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ANALYTICAL PHASE
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Analytical phase Competency Controls Methodology Procedures
Monitoring of equipment Monitoring of materials Test validation
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POSTANALYTICAL PHASE
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Postanalytical phase Result reporting Result interpretation
Result distribution
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QUALITY CONTROL (QC) EXTERNAL INTERNAL
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Non-analytical Quality Control (Para-analytical Factors)
Patient preparation Proper sample selection Proper collection and transportation Details of the patient and specimen identification Proper recording of results and their interpretation Knowledge of normal range of results and abnormalities
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Selection of appropriate samples
An appropriate sample should be collected in an appropriate way, e.g.: for diagnosing an acute intestinal amoebiasis, it is essential to examine the stool sample within minutes since trophozoites survive for that much time only. Similarly examining stool samples for the eggs of Enterobius vermicularis is not as effective as a perianal swab. Microfilaria showing nocturnal periodicity should be sampled at night only.
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Analytical Internal Quality Control
Equipment reliability Reagent stability, integrity and efficiency Adequate calibration Procedure reliability in terms of Precision Accuracy Analytical specificity
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Internal QC
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Postanalytical quality control
Any possible remarks on the results obtained should also be entered, as well as the normal range of the results. The significance of the results obtained should be highlighted wherever required There should be frequent dialogue between the laboratory personnel and the physicians for appropriate use of the facilities and the right interpretation of results obtained in the laboratory Plausibility (Hal yang masuk akal)
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THANK YOU
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