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مشروع إعتماد معمل الكمياء الإكلينيكيه – مستشفى الطوارئ

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Presentation on theme: "مشروع إعتماد معمل الكمياء الإكلينيكيه – مستشفى الطوارئ"— Presentation transcript:


2 مشروع إعتماد معمل الكمياء الإكلينيكيه – مستشفى الطوارئ

3 Role of clinician in lab result accuracy
Prof/Azza abd al baky

4 Introduction Three phases of laboratory testing: pre-analytical, analytical and post-analytical Pre-analytical—specimen collection, transport and processing Analytical—testing Post-analytical—testing results transmission, interpretation, follow-up, retesting.

5 Pre-analytical errors
Pre- and post-analytical errors are estimated to constitute 90% of errors Errors at any stage of the collection, testing and reporting process can potentially lead to a serious patient misdiagnosis Errors during the collection process are not inevitable but can be prevented with a diligent application of quality control, continuing education and effective collection systems.

6 The steps of the preanalytical phase
Preparation prior to sampling Sampling/handling Storage/transport Preparation prior to analysis

7 Implications of errors
Errors made in the period prior to the analysis of the sample ... may influence the quality of the final measured results ... and compromise the diagnosis and treatment of the patient No result is better than bad result

8 Complex and labor intensive
The more steps involved in a process, the more likely there will be errors committed % of all test errors occur in the preanalytical phase Stankovic 2008 “Quality Improvements in the Preanalytical Phase: Focus on Urine Specimen Workflow”

9 Effects of Pre-analytical Variables on the Quality of Laboratory Testing
Paying close attention to the preanalytical variables associated with blood collection is critical in ensuring accurate test results in all areas of the clinical laboratory.

10 The Pre-Analytical process
Patient Identification Sampling Technique Test Collection Procedures Specimen Transport Specimen Processing

11 The Pre-Analytical process
Collect Sample: Locate Patient Prep Patient Draw Sample Label Dispose of supplies

12 Patient identification
When identifying the patient, have them provide their full name, address, identification number and/or date of birth. Hospital No inpatients should be wearing an identification band with the above information, which the phlebotomist should confirm before the venipuncture.

13 Effects of Pre-analytical Variables on the Quality of Laboratory Testing
Patient Identification: It is important to identify a patient accurately so that blood is collected from the correct person. Drawing blood from the wrong person, or labeling the correct patient’s sample with a different patient’s label can certainly contribute to laboratory error. (Mislabeling ???)

14 Factor affecting lab result
Some patient variables that affect test results Age Genetic variation Gender Nutrition status Diet Diagnostic and therapeutic Drugs procedures(PR&endoscopy) Exercise Obesity Posture Biorythm Haemolysis,lipemia Special habits & icterus

15 Test Collection Timing of Collection Therapeutic Drug Monitoring
Peak and trough collection times Basal State Collections Fasting requirements—no food or liquid except water(10-12h) 2h postprandial, from the start of food . Specimens affected by time of day, for example, cortisol, iron and TSH.

16 Phlebotomy Phlebotomy is a highly complex skill requiring expert knowledge, and critical judgment venipuncture is a frequent medical procedure. Phlebotomy errors may cause harm to patients or result in needle stick injury to the phlebotomist

17 Error Prevention Phlebotomy Education
Phlebotomists should have completed a standard academic course in phlebotomy and undergo thorough on-the-job training under the supervision of a senior phlebotomist Continuing Education Phlebotomists should participate in regular educational competency assessments (written and observational) Professional Licensure Phlebotomy Staffing Adequate staffing to maintain collection standards Technology Use of barcode scanners for patient identification

18 1-posture: 2- collection site.
The patient should be comfortably seated or supine for 20 minutes before sampling.Not standing The patient arm should be extended in a straight line from the shoulder to the wrist. 2- collection site. The median cubital vein is the preferred site. Veins on the hand or at ankle may be used. Avoid the arm with: Extensive scarring or hematoma .,infection , edema ,burn , Containing I.V. access for I.V. infusion. On the side of mastectomy.

19 Phlebotomy Technique Correct collection system Venous access
Evacuated tube system (Vacutainer) for large veins in antecubital fossa Syringe for small, fragile veins or veins outside antecubital fossa Venous access Needle entry should be at 15 to 30 degrees depending on depth of vein Needle entry should be in same direction as vein, centered over vein Anchor vein to prevent movement during needle entry and to reduce pain to patient


21 Phlebotomy Technique Errors
Tourniquet Application Tourniquet tied too close to the venipuncture site can cause hematoma Veins may not become prominent if tourniquet is tied too high (more than 3 to 4 inches above venipuncture site) Tourniquet left on longer than one minute can result in hemoconcentration , affecting some test results Tourniquet should be released as soon as needle is in the lumen of the vein and blood flow established

22 Phlebotomy Technique Cleansing of venipuncture site
Thorough cleaning with alcohol Allow alcohol to dry completely to avoid stinging sensation upon needle entry and hemolysis of sample Samples such as blood cultures should be collected using iodine to cleanse site to ensure sterility of sample Recollection rate for blood cultures ranges due to contamination is as high as 50% in hospitals with increased costs, patient overtreatment

23 Test Collection Additive : EDTA,citrat, lithium heparin ,oxalate,flourid Hemolysis Blood collected insufficient to amount of additive in tube, Traumatic venipuncture Blood collected from area with hematoma Vigorous shaking of tubes after collection Milking the site when collecting capillary samples and blood collected using a small diameter needle.

24 Test Collection Capillary Collections—finger stick or heel stick
Appropriate site Heel stick—sides of the bottom surface of the heel Finger stick—third or fourth fingers, perpendicular to fingerprint lines on fleshy pads on finger surface Warming—Warm before collection to increase capillary blood flow near skin surface Cleaning—cleanse site with alcohol and allow to air dry Discard first drop of blood.

25 Recommended order of draw (NCCLS):
Blood Culture Bottles (Aerobic-Anaerobic) Coagulation Tube Serum Tube with or without clot activator, with or without gel separator Heparin Tube with or without gel plasma separator EDTA Glycolytic Inhibitor

26 Correct Specimen Volume: All blood collection tubes need to be filled to the correct volume. This will ensure the proper amount of blood for the amount of additive in the tube (blood to additive ratio). For example, if a 5 mL draw heparin tube is only filled with 3 mL of blood, the heparin concentration is erroneously high and may potentially interfere with some chemistry analytes, tube for Coagulation Studies incomplete filling results in specimen dilution and erroneous Prothrombin and aPTT test results.

27 Proper Tube Mixing: All tubes with additives need to be inverted to mix the additive evenly with the blood. Improper mixing of the tube after venipuncture could contribute to sample clotting.

28 E) Specimen transport Temperature Light

29 Transport Errors Temperature Transport Container
Specimens must be transported at the appropriate temperature for the required test On ice—ABGs, Ammonia Warmed -- (37 C), cryoglobulins Avoid temperature extremes if transported via vehicle from other collection site Transport Container Some samples need to be protected from light, for example, bilirubin Transport in leak-proof plastic bags in lockable rigid containers ,avoid agitation.

30 Blood Specimen Transport
Transport of blood specimens in the proper manner after collection ensures the quality of the sample Timing Some specimens must be transported immediately after collection, for example Arterial Blood Gases. Specimens for serum or plasma chemistry testing should be centrifuged and separated within two hours

31 Special Handling of Blood Specimens: Certain chemistry analytes will require the tube of blood to be chilled after collection in order to maintain the stability of the analyte. A slurry of ice and water is recommended for chilling the tubes of blood. Examples : adrenocorticotropic hormone (ACTH), angiotensin converting enzyme (ACE), acetone, ammonia, catecholamines, free fatty acids, lactic acid, pyruvate and renin ,PTH

32 Blood gases analysis “Collection of a blood specimen, as well as its handling and transport, are key factors in the accuracy of clinical laboratory analysis and ultimately in delivering quality patient care” ”Arterial blood is one of the most sensitive of the specimens sent to the clinical laboratory for analysis” ”Blood gas and pH analysis has more immediacy on patient care than any other laboratory determination” ”In blood gas and pH analysis an incorrect result can often be worse for the patient than no result at all”

33 What is so special about blood gases?
NOT like other blood samples STAT parameters Short Turn Around Time Must be analyzed within a short time pO2, pCO2, pH, LAC, GLU Valuable results right now Not in one hour Sample composition changes Patient status changes

34 Some points to keep in mind - sampling from A-lines
Preparation prior to sampling Label the sampler with patient ID Use dry electrolyte balanced heparin Endeavor to keep the patient’s respiratory condition stable for a certain period prior to sampling Make sure that the a-line has been adequately cleared of flush solution Aspirate the sample slowly to prevent degassing and hemolysis Expel any air bubbles immediately after sampling Mix the sample thoroughly with heparin after sampling Sampling/handling

35 Storage/transport Analyze sample immediately
If storage is unavoidable, store the sample at room temperature for max. 30 min. Samples with expected high pO2 values should be analyzed within 5 min. Storage/transport Before transferring the sample into the analyzer mix thoroughly Visually inspect the sample for clots and air bubbles Enter patient ID in analyzer logs Preparation prior to sample transfer

36 Stabilization of the respiratory condition
To get a true picture of the patient’s respiratory condition the patient should ideally be in a steady state of ventilation Patients should be at rest for 5 min Ventilatory settings should be unchanged for 20 min Pain and anxiety from arterial puncture may influence the steady state of respiration and should thus be minimized

37 Storage recommendations
General storage recommendation Do not cool the sample Analyze within 30 minutes For samples with high pO2 Analyze within 5 minutes For special studies, e.g. shunt For samples with high leukocyte or platelet count Expected delayed analysis When analysis is expected to be delayed for more than 30 minutes, the use of glass syringes and storage in ice slurry is recommended Storage and transport time should be kept at a minimum Volatile nature of gases Continued metabolism in blood For parameter panels including GLU/LAC, be aware that 30 minutes storage might lead to biased results It is recommended by the NCCLS to avoid cooling of samples when kept in plastic Plastic syringes are not impermeable to gas diffusion, and will allow exchange of oxygen and carbon dioxide with the ambient air. When the sample is cooled, the blood can dissolve more gas, I.e. a cooled, stored sample will potentially take up enough oxygen to bias the sample.

38 Continued cellular metabolism in sample
pO2 since oxygen will still be consumed pCO2 since carbon dioxide will still be produced pH primarily due to the change in pCO2 and glycolysis cCa2+ since the change in pH will influence the binding of Ca2+ to protein cGlu since glucose will be metabolized cLac due to glycolysis Metabolically active cells, such as leukocytes and thrombocytes, will continue to metabolize O2 to CO2 The fall in pO2 is accelerated if the original sample pO2 is high High levels of leukocytes, such as found in leukemic patients, may cause a significant fall in pO2 in a short period of time

39 Slowing down the metabolism
pO2 Blood gas samples in glass samplers can be cooled Storing the sample at a lower temperature (0-4 °C) will slow down the metabolism by at least a factor of 10 [NCCLS] Cool samples in an ice slurry or other suitable coolant Never store the samples directly on ice as this causes hemolysis of the blood cells Time 0-4 C 25 C NCCLS Document C27-A; Blood Gas Pre-Analytical Considerations: Specimen Collection, Calibrations and Controls; Approved Guideline

40 Potential preanalytical errors
Preparation prior to sampling Missing or wrong patient/sample identification Use of the wrong type or amount of anticoagulant - dilution due to the use of liquid heparin - insufficient amount of heparin - binding of electrolytes to heparin Inadequate stabilization of the respiratory condition of the patient Inadequate removal of flush solution in a-lines prior to blood collection

41 Sampling /handling Mixture of venous and arterial blood during puncturing Air bubbles in the sample Insufficient mixing with heparin Incorrect storage Hemolysis of blood cells Storage and transport Visually inspect the sample for clots Inadequate mixing of sample before analysis Failure to identify the sample upon analysis Prep prior to transfer

42 Mixture of venous and arterial blood
When puncturing an artery it is important not accidentally to get the arterial blood mixed with venous blood This may, for instance, occur, if you hit a vein before locating the artery Even an admixture of a small amount of venous blood may significantly bias the results This is especially true of pO2 and sO2, but other parameters may also be affected Vein Artery 40 mmHg / 5.3 kPa 100 mmHg / 13.3 kPa

43 Mixture of venous and arterial blood
In arteries the blood pressure is high enough to fill a self-filling syringe If a self-filling syringe does not fill it may be because a vein has been hit In that case a new sample should be taken Vein: Pressure rarely > 10 mmHg Self-filling syringes typically fill upon a pressure of 20 mmHg Artery: Systolic blood pressure normally > 100 mmHg

44 Inadequate removal of flush solution
Flush solutions used in a-lines must be removed completely from the system to avoid a dilution of the blood sample It is recommended to withdraw a volume equal to three to six times the “dead space” of the catheter system (NCCLS)

45 Inadequate removal of flush solutions
Sample B and A are both a-line samples taken from the same patient immediately after each other Before taking sample B only 1 mL of saline solution was removed - the tubing, however, looked red Before taking sample A saline solution was removed as recommended Sample A ctHb 6.2 mmol/L cGlu 9.6 mmol/L cK+ 3.8 mmol/L cNa+ 130 mmol/L cCa mmol/L cCl- 101 mmol/L pH 7.271 pCO mmHg / 6.7 kPa pO mmHg / kPa Sample B ctHb 4.6 mmol/L cGlu 6.9 mmol/L cK+ 2.5 mmol/L cNa+ 137 mmol/L cCa mmol/L cCl- 113 mmol/L pH 7.275 pCO mmHg / 4.8 kPa pO mmHg / 17.2 kPa Saline solution is kept in a plastic bag which is permeable to air. Oxygen and carbon dioxide equilibrates with the ambient air and thus represents high tensions.

46 Air bubbles Any air bubbles in the sample must be expelled as soon as possible after the sample has been drawn before mixing the sample with heparin before any cooling of the sample Even small air bubbles may seriously affect the pO2 value of the sample, normally resulting in increased values An air bubble whose relative volume is 0.5 to 1.0 % of the blood in the syringe is a potential source of a significant error

47 Effect of air bubbles - an example
Sample A and B were taken from the same patient immediately after each other Sample A without air bubbles was analyzed immediately after collection 100 µL air was added to sample B (1 mL). It was stored cold (0-4 °C) for 30 minutes and mixed for 3 minutes before sample analysis Sample A pO mmHg / 38.5 kPa (FIO ) Sample B pO mmHg / 33.8 kPa (FIO )

48 Insufficient mixing with heparin
Insufficient mixing can cause coagulation of the sample It is recommended to mix the blood sample thoroughly with heparin Invert the syringe 10 times and roll it between your palms Red blood cells tend to stack (like coins or plates) due to their concave shape. Stacking is prevented by mixing in two dimensions.

49 Inadequate mixing - an example
Sample A and B were taken from the same patient immediately after each other and stored cold for 10 minutes Sample A was mixed in a rotator (14 revolutions/min) for 3 minutes Sample B was mixed in a rotator (14 revolutions/min) for 1 minute Sample A ctHb 6.2 mmol/L Sample B ctHb 4.5 mmol/L

50 Hemolysis of blood cells
The blood cells are relatively fragile, and therefore hemolysis may easily occur during blood sampling Hemolysis may, for instance, occur due to high filling pressure through a narrow entrance (e.g. during too vigorous sample aspiration, sample transfer to the analyzer, etc.) vigorous rubbing or squeezing of the skin during capillary sampling too vigorous mixing of the sample cooling down the sample below 0 °C

51 “The weak link” Blood gas analyzers of today are highly accurate
Make sure that sample represents patient status The preanalytical phase is the weak link in the Patient Focus Circle Many potential errors Can be overcome by Training User guidelines Sampling products BG Analyzers of today are highly accurate. The results reflect the composition of the sample – i.e. make sure that the sample represents the patient! Studies have shown that up to 60% of all errors in blood sampling are related to the preanalytical phase. Conclusion: need for training and samplers that are easy to use and do not introduce errors.

52 Specimen Quality Markers for Rejection
Clotted Hemolyzed Underfilled, overfilled Insufficient quantity Incorrect labeling Unlabeled specimen Incorrect patient Incorrect specimen Contaminated Lost sample Too old to process Broken and leaking

53 Finally… The human role in sample collection makes complete elimination of errors associated with laboratory testing unrealistic However, good practices and compliance with the new strategies for error prevention can lead to a substantial reduction in pre-analytical errors.



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