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Quality in Laboratory Hemostasis and Thrombosis (eBook, PDF)

Show more about author. The essential elements of a quality program, specifically internal quality control IQC and external quality assurance EQA , should be applied to each laboratory assay performed in order to ensure test result accuracy and precision.

The coagulation laboratory plays an important role in the diagnosis and treatment of individuals with bleeding or clotting i. Test methodologies used to assess common disorders or diseases of haemostasis are reviewed as well as the clinical relevance of each assay. The preanalytical phase of testing offers the greatest opportunity for introducing result error in the haemostasis laboratory and it is therefore imperative that samples are properly collected, transported and stored.

Samples for haemostasis testing should be collected in 3. Some test processes such as platelet function testing have special processing and testing requirements. For plasma-based tests, centrifugation to obtain platelet poor plasma and testing should ideally be completed within 4 hours or the plasma frozen. IQC must be performed with each assay, at appropriate levels of the analyte and at appropriate time intervals as a means for assessing ongoing assay performance.

EQA, a peer group assessment process that is supplementary to IQC, offers in addition the opportunity for evaluation of long-term performance of laboratories, including comparisons with like and unlike methodologies, and often serves as an educational resource. Participation in an EQA program is often a requirement of laboratory accreditation and there are a multitude of EQA organizations that offer programs specific to haemostasis testing with international programs providing assessment of the more specialized haemostasis assays.

These programs provide invaluable information on assay specific diagnostic error rate, assay precision, accuracy, sensitivity and assessment of overall assay performance. The incorporation of IQC and EQA into a laboratory program can not only assist in the assurance that testing is reliable and accurate but also improve the quality of the testing.

DOI: Categories: Special issue. Journal Volume 20 June, Issue 2 Quality in coagulation and haemostasis testing. Quality in coagulation and haemostasis testing. Roslyn Bonar [ 1 ] Emmanuel J. One particular publication 2 from the Clinical Laboratory Standards Institute CLSI previously known as the National Committee for Clinical Laboratory Standards NCCLS identifies several major activities of importance to a laboratory quality program, including personnel development, equipment choice and operation, process improvement, and safety.

Also listed are two other essential elements that are the primary focus of the current report, namely internal quality control IQC and external quality assurance EQA for individual test processes. In addition to IQC and EQA, the current report also briefly mentions extra-analytical issues and reflects on some key guidelines available from various expert bodies to ensure performance of optimal testing within the field of haemostasis.

The development of these critical elements helps to ensure that the data reported by the laboratory are as accurate as possible and that they best serve the needs of both patients and clinicians 3—7.

These components work in concert. When any phase of this process is disturbed, adverse clinical events may occur, manifesting as either thrombosis haemostasis pushed in a procoagulant direction or bleeding ineffective haemostasis.

In either situation, the clinician must have access to a variety of relevant tests in order to achieve a specific or correct diagnosis and initiate appropriate patient treatment or management.

Primary haemostasis refers to the process that involves platelets adhering to each other and to the damaged vasculature subsequent to the initiating event e. The process of secondary haemostasis in part acts to strengthen the platelet plug, forming a gel-like clot. This process is kept in check, in part, by the naturally occurring anticoagulant system, e. The fibrinolytic system represents a distinct, but inter-related process that is involved in lysis of the clot to facilitate wound healing.

These disorders of haemostasis can be either inherited i. In order to screen, diagnose and monitor these disorders, the modern haemostasis laboratory must be equipped with an arsenal of tests to allow accurate and complete diagnoses.

Haemophilia is caused by a deficiency of usually one and rarely several clotting factors, which may arise congenitally or may be acquired. Haemophilia A is approximately seven times more common than Haemophilia B.

As congenital disorders, both reflect sex-linked recessive disorders as the defective genes are carried on the X chromosome. VWD is another bleeding disorder that arises from deficiencies or defects in the plasma protein von Willebrand factor VWF It usually presents with mild bleeding tendencies such as epitasis and easy bruising and most often has a congenital nature but may alternatively be acquired.

VWF is stored primarily in the platelets and endothelial cells and has two main functions within haemostasis 8. Firstly, VWF mediates the formation of the platelet haemostatic plug by acting as the main adhesive protein that bridges platelets to the damaged vasculature as well as to other platelets.

VWF functions in this manner by means of specific interactions with extracellular matrix components such as collagen, specific interactions with various platelet receptors, and a specific interaction with FVIII 8, VWF is thus essential for both the initial tethering of platelets to the damaged vasculature i.

In plasma, VWF comprises a series of dimer proteins of increasing size or molecular weight ; the larger the size or molecular weight , the more adhesive the molecule. A host of platelet defects can also lead to mucocutaneous bleeding or bruising 11— Thrombophilia can be defined as an increased risk of thrombosis and can be hereditary or acquired.

Laboratory testing of thrombophilia requires a panel of test procedures that can be molecular-based, functional or antigenic in nature. A wide variety of disorders can give rise to a thrombophilic tendency, including deficiencies or defects in the natural anticoagulant proteins i. Acquired predisposition to thrombosis can also occur in many disease states, and one of the most important and common is the auto-immune disorder called the antiphospholipid antibody syndrome APS , which arises due to the presence of antiphospholipid antibodies aPL , detectable in the laboratory using a variety of tests including those for Lupus Anticoagulant LA , anticardiolipin antibody aCL and anti-Beta2-glycoprotein-I aB2GPI antibodies 18, The modern haemostasis laboratory performs an arsenal of tests to allow an accurate and comprehensive diagnosis of haemostatic defects.

Some tests are also used to monitor anticoagulant therapy. First proposed by Quick in 20 , the PT is perhaps the oldest test of coagulation still performed.

The test is performed by adding tissue factor and phospholipids to plasma and then measuring the time in seconds to clot formation following the addition of calcium. Originally developed to measure prothrombin one of the procoagulant factors and hence its name , the PT is also now known to measure other aspects of the coagulation pathway such as the interaction of FV, FVII, FX and the concentration and function of fibrinogen.

The APTT is also used for monitoring of heparin therapy and is variously sensitive to several inhibitors including LA In all the above cases, one expects to see a prolongation in the APTT. In contrast, a shortened APTT is associated with an increased thrombosis risk 23— The activator in this test can be from several sources. Originally kaolin was used hence, the test was previously called PTTK but in more recent times activators such as micronized silica and ellagic acid have been substituted.

The APTT is the time to clot in seconds when contact activator and phospholipids are added to plasma in the presence of calcium. This is a simple test performed by adding equal volumes of plasma and thrombin and measuring the amount of time until a clot forms.

This represents the major clottable protein within plasma, and was originally measured by heat precipitation. These days, fibrinogen is measured immunologically or more commonly using a functional von Clauss assay, which can be easily automated.

Fibrinogen levels can also be estimated using a derived calculation from the PT with selective instrumentation. The measurement of fibrinogen is important within the context of potential congenital abnormalities such as afibrinogenaemia and dysfibrinogenaemia perhaps strangely, these may be associated with both bleeding and thrombosis 26,27 , as well as in the context of trauma, snake bite, and disseminated intravascular coagulation DIC This represents a specific breakdown fragment of fibrin, and so is a measure of fibrinolysis.

This test is important in order to assess the possibility of clot dissolution as a marker of thrombosis; e. These are performed by modifications of PT or APTT assays, using several plasma dilutions, in order to pinpoint specific factor deficiencies e. Tests are made individually specific for any given factor by using the particular factor deficient plasma. The exception here is FXIII, or the fibrin stabilising factor, which is measured using alternate techniques These comprise a panel of tests, primarily to help evaluate for a bleeding disorder such as VWD 32 , although VWF is also being increasingly requested within the context of thrombotic disease Some assays measure the quantity of VWF present in plasma i.

This can be achieved using comprehensive platelet aggregation testing 11—14 or using a screening test process e. The latter can be used to provisionally identify a platelet defect, or anti-platelet medication affect e. Laboratory testing may include assays to detect congenital deficiencies or defects in the natural anticoagulants i. One of the most common and clinically important causes of acquired thrombophilia, APS, is assessed by a panel of tests that measure aPL autoantibodies that recognize epitopes on selected proteins when bound to phospholipid surfaces.

More clinically important is that these patients can suffer serious bleeding problems While some patients can develop inhibitors after treatment with plasma products e.

After an inhibitor is identified through mixing studies in a routine coagulation test system i. There are many steps in the process of laboratory testing where the process can go awry and therefore must be controlled. In order to ensure the appropriateness of test results, laboratories are required to put several quality processes into place, and namely to undertake performance of both internal quality control IQC and external quality assurance EQA.

Quality control provides a process to monitor a number of variables that may include pre-analytical, analytical, post-analytical and interpretative error. For example, there are a vast number of pre-analytical variables in haemostasis. These are often beyond the control of the test laboratory, and are not always easily identifiable. As detailed below, they comprise issues that occur prior to testing and include specifics related to collection e. Pre-analytical issues can lead to serious adverse affects on the test and thus subsequent patient care 7.

Laboratory data must be accurate and reliable as erroneous results may lead to patient misdiagnosis and therefore therapeutic misadventures. Inaccuracy in laboratory reporting can arise due to problems introduced at any point in the testing process, from sample collection to report results. Due to significant advances in instruments and informatics, the analytical and reporting phases of testing do not contribute significantly to laboratory error.

Rather, the pre-analytical phase of testing represents the major source of inaccurate laboratory results 48, One of the most critical aspects of specimen collection is proper patient and also sample identification. Samples should be collected in a relatively atraumatic fashion and blood should flow freely into the specimen container.

Samples for haemostasis testing should be anticoagulated with sodium citrate. It is important that the concentration of sodium citrate is consistent within a laboratory system as clotting times tend to be longer in 3. Samples for haemostasis testing that contain visible clots should not be analyzed and must be rejected. The required blood to anticoagulant ratio is and therefore overfilling or underfilling of the evacuated tube should be avoided as this can introduce result error.

Other anticoagulants such as ethylenediaminetetraacetic acid EDTA or heparin are not acceptable for haemostasis testing.

Samples collected in EDTA or heparin anticoagulated tubes or the use of serum for haemostasis testing will lead to aberrant results and this can cause clinically significant errors in patient diagnosis.

Some laboratories receive a portion or majority of test samples in secondary aliquot tubes and in this instance, the sample types are indistinguishable unless clearly and properly labeled as sodium citrate plasma, EDTA plasma, heparin plasma or serum.

When the sample matrix is unknown or in doubt, performance of sodium, potassium and calcium assays on the sample can be undertaken to help determine the sample matrix. Samples collected in sodium citrate tend to have high sodium and low calcium values while samples collected in potassium EDTA will have elevated potassium levels with undetectable calcium values Samples for haemostasis testing collected in the wrong anticoagulant tube or serum samples should not be analyzed and must be rejected.


Wiley Online Library Probekapitel. The hemostasis laboratory has a vital role in the diagnosis and management of patients with familial and acquired haemorrhagic and thrombotic disorders. Its role in the monitoring of traditional anticoagulant therapy, as well as therapy using new anticoagulants, presents new challenges to the laboratory. This new edition addresses these important issues, as well as international guidelines for testing, the development of international standard materials, management of haemostasis testing from the laboratory to the point-of-care, and molecular genetic testing. Preis inkl.

The premise of this concept was to improve all phases of laboratory testing, specifically pre-analytical, analytical and post-analytical processes. Hemostasis testing is particularly sensitive to pre-analytical issues, including sample collection, handling, transportation, processing and storage 2. Each of these steps needs to be addressed and controlled locally with proper, consistent institutional procedures and protocols to minimize pre-analytical errors. Quality assurance measures specific for the analytical phase of hemostasis testing occurs: I during the initial test evaluation method validation of test performance ; II as part of periodic quality control QC daily or as required QC performance ; and III during episodic assessment using external quality assurance EQA, also commonly referred as Proficiency Testing. According to the College of American Pathologists CAP , the benefits of participation in an EQA program include improving laboratory practice, characterizing local test performance over site specific and multiple platforms, identifying potential test interferences e.

2008, Number 3

Quality Assurance in the laboratory ensures that the result a laboratory generates and reports is accurate, precise and specific. External quality assurance EQA is an important component of the total quality assurance program of a clinical haemostasis laboratory. The same test, performed on the same specimen, should give the same answer wherever and by whoever it is carried out.

Quality in coagulation and haemostasis testing

Pre-analytical issues in the haemostasis laboratory: guidance for the clinical laboratories

Olson , F. Professor Preston has been a co-author on more than publications in peer reviewed journals in the field of hemostasisand thrombosis. He is the head scientist at theSheffield Haemostasis and Thrombosis Centre. He has 25 yearsexperience in the field of laboratory testing in haemostasis with along standing interest in standardisation and has been involved indrawing up guidelines for a number of National and Internationalbodies in the field.

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Quality in Laboratory Hemostasis and Thrombosis. Second Edition. Edited by. Steve Kitchen, Clinical Scientist, Sheffield Show all.

Quality in Laboratory Hemostasis and Thrombosis

Assessing EQA: pre-analytical issues

Next Quality in Laboratory Hemostasis and Thrombosis. Quality in hemostasis and thrombosis--part III. Quality in laboratory hemostasis and thrombosis second edition edited by steve kitchen, clinical scientist, sheffield haemophilia and thrombosis centre. The coagulation laboratory offers a wide variety of testing to aid in the diagnosis the quality of test General quality planning in the hemostasis laboratory John D. Hemostasis test validation, performance, and reference intervals international recommendations and guidelines Richard A. Causes of errors in medical laboratories Giuseppi Lippi, Emmanuel J. Laboratory evaluation of hemostasis and thrombosis Sep 05, Posted By John Grisham Library TEXT ID bc8ea Online PDF Ebook Epub Library hemostasis and thrombosis philadelphia lea febiger ocolc document type book all authors contributors marjorie s sirridge reaner shannon laboratory Quality in Laboratory Hemostasis and Thrombosis has been completely revised and updated to reflect the changing process of managing quality.

Metrics details. Ensuring quality has become a daily requirement in laboratories. In haemostasis, even more than in other disciplines of biology, quality is determined by a pre-analytical step that encompasses all procedures, starting with the formulation of the medical question, and includes patient preparation, sample collection, handling, transportation, processing, and storage until time of analysis. This step, based on a variety of manual activities, is the most vulnerable part of the total testing process and is a major component of the reliability and validity of results in haemostasis and constitutes the most important source of erroneous or un-interpretable results. Pre-analytical errors may occur throughout the testing process and arise from unsuitable, inappropriate or wrongly handled procedures. Problems may arise during the collection of blood specimens such as misidentification of the sample, use of inadequate devices or needles, incorrect order of draw, prolonged tourniquet placing, unsuccessful attempts to locate the vein, incorrect use of additive tubes, collection of unsuitable samples for quality or quantity, inappropriate mixing of a sample, etc. Some factors can alter the result of a sample constituent after collection during transportation, preparation and storage.

Show more about author. The essential elements of a quality program, specifically internal quality control IQC and external quality assurance EQA , should be applied to each laboratory assay performed in order to ensure test result accuracy and precision. The coagulation laboratory plays an important role in the diagnosis and treatment of individuals with bleeding or clotting i. Test methodologies used to assess common disorders or diseases of haemostasis are reviewed as well as the clinical relevance of each assay. The preanalytical phase of testing offers the greatest opportunity for introducing result error in the haemostasis laboratory and it is therefore imperative that samples are properly collected, transported and stored.

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Ama C. 13.05.2021 at 08:55

Hemostasis is a delicate, dynamic and intricate system, in which pro- and anti-coagulant forces cooperate for either maintaining blood fluidity under normal conditions, or else will prompt blood clot generation to limit the bleeding when the integrity of blood vessels is jeopardized.