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1.qualitycontrol final
- 3. Three principles ofclinical lab
- 4. What is Quality? Qualitydefined as conformance to the requirements of users or customers
- 5. Total quality managementof the clinical lab
- 6. Quality Control Emphasizes statisticaland nonstatistical check procedures Able to detect the problems early enough to prevent their consequences Techniques and procedures that monitor performance parameters
- 7. Prerequisite for aneffective lab service Promotion of quality control and continuous improvement of the total testing process, including preanalytical and postanalytical phases
- 8. Steps in obtaininga laboratory test
- 9. Lab testing processesand their potential errors Test ordering Specimen acquisition Analytical measurement Test reporting Test interpretation
- 10. Test ordering Inappropriate test Handwritingnot legible Wrong patient identification Specimen acquisition Analytical measurement Test reporting Test interpretation Lab testing processes and their potential errors
- 11. Test ordering Specimen acquisition Incorrect tube Incorrectpatient identification Inadequate volume Collected at wrong time Improper transport conditions Analytical measurement Test reporting Test interpretation Lab testing processes and their potential errors
- 12. Test ordering Specimen acquisition Analytical measurement Instrument not calibratedcorrectly Specimen mix-up Incorrect volume of specimen Interfering substance present Instrument precision problem Test reporting Test interpretation Lab testing processes and their potential errors
- 13. Test ordering Specimen acquisition Analytical measurement Test reporting Wrongpatient identification Report not legible Report delayed Transcription error Test interpretation Lab testing processes and their potential errors
- 14. Test ordering Specimen acquisition Analytical measurement Test reporting Testinterpretation Interfering substance not recognized Specificity of the test not understood Precision limitations not recognized Analytical sensitivity not appropriate Previous values not available for comparison Lab testing processes and their potential errors
- 15. Elements of aQA/QC Program Commitment Facilities and resources Technical competence Technical procedures Problem solving mechanisms
- 16. Quality Control: TechnicalProcedures Control of preanalytical variables Control of analytical variables Control of analytical quality using statistical methods and control charts
- 17. Test requests Patient preparation Patientidentification Specimen acquisition Specimen transport Specimen processing Specimen distribution Preparation of work lists Control of preanalytical variables
- 18. Patient Identification The highest frequencyof errors occurs with the use of handwritten labels and request forms. The use of bar code technology has significantly reduced ID problems. Turnaround time Delayed and lost test requisitions, specimens and reports can be major problems for labs. Recording of the actual times of specimen collection, receipt in the lab and reporting of results with use of computers will solve these problems.
- 19. Manual entry ofdata even with the double checking of results Computerization will reduce this type of transcription error. Lab tests are affected by many factors, such as, recent intake of food, alcohol, or drugs; smoking, exercise, stress, sleep, posture during specimen collection The lab must define the instructions and procedures compliance with these instructions can be monitored directly efforts should be made to correct non compliance
- 20. • Prolonged tourniquetapplication. • Blood collection from an arm into which an intravenous infusion is running. Specimen Collection • To monitor and control these problems, specially trained lab team assigned to specimen collection • The identification of the person collecting a specimen should be maintained • Clinicians should be encouraged to report clinically inconsistent results. Hemolysis during blood collection
- 21. Analytical methodology Standardization Calibration procedures Documentationof analytical protocols Monitoring of critical equipment and materials Control of analytical variables
- 22. • Water quality •Calibration of volumetric glassware and pipets • Stability of electrical power • Stability of temperature of heating baths, refrigerators, freezers and centrifuges Many analytical variables
- 23. •Procedure name •Clinical significance •Principleof method •Specimen of choice •Reagents and equipments The procedure Manual should contain the following
- 24. • • Procedure • Referencevalues • Comments • References The procedure Manual should contain the following
- 25. • Values covermedical decision points • Similar to the test specimen (matrix) • Available in large quantity • Stored in small aliquots • Ideally, should last for at least 1 year Using stable ‘controls’
- 26. • Reconstitute lyophilizedmaterial carefully & strictly as per label direction • Frozen sample to be thawed properly. After attaining room temp., mix slowly by inversion and then use. • Storage temperature to be strictly followed Precautions to be followed
- 27. Assayed Unassayed Level 1 ,2 and 3
- 28. • Have aknown concentration of the substance (analyte) being measured • Used to adjust instrument, kit, test system in order to standardize the assay • Sometimes called a standard, although usually not a true standard • This is not a control Using ‘Calibrators’
- 30. Day to dayinternal QC programme Is a most useful tool For maintenance of long term Consistency ( Accuracy ) control Long term Precision control of analytical method Internal Q C monitors a single lab
- 31. Provides independent validationof internal QC program Gives valid estimation of long term accuracy of analytical system Compares performance of different labs
- 32. Control of analyticalquality using statistical methods and control charts Statistical methods Mean, SD, CV Accuracy Precision Control charts Levey-Jennings Control Chart Westgard multirule chart Shewhart SD control chart
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- 37. Strandard Deviation • Instatistics and probability theory, the standard deviation (SD) (represented by the Greek letter sigma, σ) shows ; • how much variation or dispersion from the average exists.
- 38. Strandard Deviation • Alow standard deviation indicates that the data points tend to be very close to the mean (also called expected value) • A high standard deviation indicates that the data points are spread out over a large range of values
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- 40. coefficient of variation •The coefficient of variation (CV) is defined as the ratio of the standard deviation to the mean
- 41. Levey-Jennings chart • Levey-Jenningschart is a graph that quality control data is plotted on to give a visual indication whether a laboratory test is working well • The distance from the mean is measured in standard deviations (SD)
- 42. Levey-Jennings chart • Onthe x-axis the date and time, or more usually the number of the control run, are plotted. • A mark is made indicating how far off the actual result was from the mean (which is the expected value for the control).
- 43. Levey-Jennings chart • Linesrun across the graph at the mean, as well as one, two and sometimes three standard deviations either side of the mean. • This makes it easy to see how far off the result was.
- 44. Control of analyticalquality using patient data Clinical correlation of test results Correlation with other lab tests
- 45. 45 Selecting Control Materials Calibrators •Has a known concentration of the substance (analyte) being measured • Used to adjust instrument, kit, test system in order to standardize the assay • Sometimes called a standard, although usually not a true standard • This is not a control
- 46. 46 Selecting Control Materials Controls •Known concentration of the analyte Use 2 or three levels of controls Include with patient samples when performing a test • Used to validate reliability of the test system
- 47. Biological Specimens • Blood •Urine • Cerebrospinal Fluid • Amniotic Fluid • Duodenal Aspirate • Gastric Juice • Gall stone • Kidney Stone • Stools • Saliva • Synovial Fluid • Tissue Specimen • Choice of specimen type depends on – Analyte to be measured – Ease of collection Comprise the majority of all specimens analyzed
- 48. Blood Composition Plasma Plasma isfluid component of blood. Comprises ~55% of total volume of whole blood. Contains proteins, sugars, vitamins,minerals, lipids, lipoproteins and clotting factors. 95% of plasma is water Red Blood cells (RBC) Whole Blood Whole Blood after centrifugation Note: clotting has been prevented White Blood cells (WBC) & Platelets Cellular Components
- 49. Blood Composition Serum Plasma isfluid component of blood. Comprises ~55% of total volume of whole blood. Contains proteins, sugars, Vitamins,,minerals, lipids, lipoproteins No clotting factors 95% of plasma is water Blood Clot -comprised of clotting factors (Fibrin,platets etc) -RBCs Whole Blood Whole Blood after clotting and centrifugation If blood is collected and allowed to stand it will clot. Formation of an insoluble fibrin clot. If blood is then centrifuged the fluid portion is known as SERUM
- 50. Blood Analysis • Source –Veins – Arteries – Skin puncture-capillary blood • Factors affecting choice of Blood Source and Collection Method – Analyte under investigation – Patient • vascular status • ease of collection • Collection Method – Syringe – Evacuated tube • Additives • Separator gel – Intravenous lines
- 51. Blood Analysis • Testingcan be done on whole blood, serum or plasma. Choice depends on a number of factors • Analyte to be measured – Most hematology tests requires whole blood • Instrumentation used for analysis – Most automated instruments are not set up for whole blood analysis • The way the test was developed. – Tests are often only validated on either plasma or serum • Turn around time – Analysis of whole blood is the quickest. No waiting for clot or spinning – Plasma requires centrifugation prior to analysis – With serum, the blood must clot then you have to centrifuge
- 52. Blood Analysis inthe Chemistry • Since most tests in the chemistry lab involve analytes that are dissolved in the fluid portion of blood, serum or plasma are the specimens of choice. • Important exceptions include – Hemoglobin, Red blood cell (RBC) Folate – Blood gases • Protein electrophoresis was developed based on the analysis of serum. Not done on plasma because of the presence of the protein fibrinogen which distorts the electrophoretic pattern. • Many tests can use either serum or plasma
- 53. Collection Tubes • Themost widely used tubes for blood collection are evacuated tubes (Vacutainers) – Negative pressure facilitates collection – Easy to use – Sterile – Universally used colour-coded rubber stoppers to denote tube type. – Tubes can contain various anticoagulants for the collection of whole blood or plasma. – Tubes can have additives for specific tests (glucose, metals)
- 54. Collection Tubes (Vacutainers) Serum SeparatorTube (SST) Separator Gel Separator Gel Serum Clot
- 55. Collection tubes • Red-toptubes contain no anticoagulants or preservatives • Red-top tubes are used for collecting serum – 10-15 minutes is required to allow blood to clot before centrifuging – Used for blood bank specimens, some chemistries
- 56. Collection tubes • Gold(and “tiger”) top tubes contain a gel that forms a physical barrier between the serum and cells after centrifugation • No other additives are present • Gel barrier may affect some lab tests
- 57. Collection tubes • Usedfor Glucose measurement. • After blood collection, glucose concentration decreases significantly because of cellular metabolism • Gray-top tubes contain either: – Sodium fluoride and potassium oxalate, or – Sodium iodoacetate • Both preservatives stabilize glucose in plasma by inhibiting enzymes of the glycolytic pathway – NaF/oxalate inhibits enolase – Iodoacetate inhibits glucose-3-phosphate dehydrogenase
- 58. Collection tubes • Green-toptubes contain either the Na, K, or lithium (Li) salt of heparin. Most widely used anticoagulant for chemistry tests. – Should not be used for Na, K or Li measurement – Can effect the size and integrity of cellular blood components and not recommended for hematology studies • Heparin accelerates the action of antithrombin III, which inhibits thrombin, so blood does not clot (plasma) • The advantage of plasma is that no time is wasted waiting for the specimen to clot
- 59. Collection tubes • Lavender-toptubes contain the K salt of ethylenediaminetetraacetic acid (EDTA), which chelates calcium (essential for clot formation) and inhibits coagulation • Used for hematology, and some chemistries • Cannot be used for K or Ca tests
- 60. Collection tubes • Blue-toptubes contain sodium citrate, which chelates calcium and inhibits coagulation • Used for coagulation studies because it is easily reversible.
- 61. Collection tubes • Brownand Royal Blue top tubes are specially cleaned for trace metal studies – Brown-top tubes are used for lead (Pb) analysis – Royal blue-top tubes are used for other trace element studies (acid washed)
- 62. Test results Variations, Errors,Interferences • Variations • Clinical variations within an individual and between individuals • Analytical variations-no test is perfect. All tests have some degree of variations for repeated measurements of the same sample. • The final test result is affected by factors that occur – Pre-analytically – At the time of the test – After the test is completed
- 63. Steps in obtaininga laboratory test • Test is requested by physician and ordered on the computer. Barcode is generated • Specimen is collected • Specimen and order are transported to the lab • The specimen is accessioned in the lab
- 64. Steps in obtaininga laboratory test • The specimen is processed • The specimen is analyzed • The results are reviewed and verified by technologists • The results are released to the patient’s record
- 65. Why Analytical ResultsVary Inter-individual Variation • Age • Sex • Race • Genetics • Long term health status Intra-individual Variation •Diet •Exercise •Drugs •Sleep pattern •Posture •Time of venipucture •Length of time tourniquet is applie
- 66. Why Analytical ResultsVary Pre-analytical Variation •Transport •Exposure to UV light •Standing time before separation of cells •Centrifugation time •Storage conditions Analytical Variation •Random errors •Systematic errors Post-analytical •Transcriptions errors •Results reported to wrong patient
- 67. Pre-analytical errors • Collection –Was the right tube used? – Was venipuncture performed correctly? – Was the specimen properly stored? • Identification – Was the blood collected from the correct patient? – Was the blood correctly labeled? • Patient name, ID, date, time of collection, phlebotomist
- 68. Specimen identification • Oneof the common sources of erroneous lab results is misidentified specimens • The lab is required to have a clear and rational policy for identifying specimens, and handling misidentified specimens
- 69. Prolonged venous stasis Blockingthe flow of blood with the tourniquet with eventually lead to a sieving effect. Small molecules, water and ions are forced out blood vessels and larger molecules are concentrated • Increases Total Protein, proteins, iron (Fe), cholesterol, bilirubin • Decreases potassium
- 70. Supine vs. sittingor standing • Going from lying (supine) to upright reduces total blood volume by about 700 ml • The following may decrease by 5-15% in the supine patient: – Total protein – Albumin – Lipids – Iron – Calcium – Enzymes
- 71. Specimens requiring specialhandling • Should be placed immediately on ice – Lactate – Ammonia – Acid phosphatase – Plasma catecholamines
- 72. Significantly affected byhemolysis: • Hemolysis-rupture of red blood cell – Can be due to improper collection – End result is dumping cellular contents into blood. Mild dilution effect in some analytes • Significant increase in potassium, magnesium, phosphorous
- 73. Interferences • Hemolysis – Therelease of hemoglobin into blood can effect the reactions comprising specific tests – Causes serum or plasma to be red and can effect tests that are colorimetric • Lipemia (lots of fats) and proteinemia (lots of protein) – Causes serum or plasma to be become turbid. This can effect colorimetric and turbidometric based tests – Also can cause a dilution effect. Fats and proteins are large and displace water in plasma. Can give falsely low results especially for Na
- 74. Interferences • Human AntiAnimal Antibodies. – Occurs in individual that have been exposed to foreign immunoglobins – Can significantly increase or decrease immunoassay based tests since all utilize animal antibodies, particularly mouse. Referred to as Human Anti Mouse Antibodies (HAMA) – Tests usually contain reagent to clear HAMA – Technicians performs a dilution test to determine if HAMA are present – Generally have to send to another lab to test by alternate method or different antibody
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- 86. Control of analyticalquality using patient data Clinical correlation of test results Correlation with other lab tests
- 87. •Tietz test bookof clinical Biochemistry •Varley •Kaplan •Internet References