Coagulation tests

Hematology. The functional status of blood and of the blood-forming tissues can be assessed by tests which include red and white blood cell counts, platelet counts, clotting time, coagulation tests, and examination of bone marrow. Such tests, in addition to detecting abnormahties, may also allow differentiation between primary and secondary effects on blood and blood-forming tissues (75). 

Blood coagulation tests are usually ordered before and during heparin tiierapy, and die dose of heparin is adjusted to die test results. Optimal results of therapy are obtained when the APTT is 1.5 to 2.5 times the control value The LMWHs do not require close monitoring of blood coagulation tests. 

Each time heparin is given, die nurse inspects the needle site for signs of inflammation, pain, and tenderness along die padiway of die vein. If these should occur, die use of diis site is discontinued and a new intermittent set is inserted at a different site Coagulation tests are usually performed 30 minutes before die scheduled dose and from die extremity opposite die infusion site... 

Blood coagulation tests for those receiving heparin by continuous IV infusion are taken at periodic intervals (usually every 4 hours) determined by the primary health care provider. If the patient is receiving long-term heparin therapy, blood coagulation tests may be performed at less frequent intervals... 

If administration of this drug is necessary, the nurse monitors the patient s blood pressure and pulse rate every 15 to 30 minutes for 2 hours or more after administration of the heparin antagonist. The nurse immediately reports to the primary health care provider any sudden decrease in blood pressure or increase in the pulse rate The nurse observes the patient for new evidence of bleeding until blood coagulation tests are within normal limits. To replace blood loss, the primary health care provider may order blood transfusions or fresh frozen plasma... 

Baseline complete blood count (CBC) and coagulation tests (activated partial thromboplastin time and International Normalized Ratio) should be obtained, as most patients will receive antithrombotic therapy, which increases the risk for bleeding. 

Preanalytical Variables Affecting Global Coagulation Tests. 157... 

Many of the coagulation factors measured by global coagulation tests have limited stability, and the time and temperature of storage of sample will affect their measurements. Concepts of analyte stability and half-life in plasma extend to markers measured by immunoassay. Markers of platelet activation are affected by artifactual activation in vitro upon collection of the blood specimen. This section will highlight some of the nonanalytical variables that, if uncontrolled, can lead to spurious results and thus affect the interpretation of laboratory data. 

The storage temperature of a specimen influences the results of coagulation tests. Generally, when plasma is stored in contact with cells and maintained at4°C for up to 7 hours, the PT is not artifactually shortened (103). However, beyond 7 hours factor VII is activated, thereby shortening the PT (104). At room temperature (25°C), provided the specimen container is well stoppered, the PT has been shown to be stable for up to 48 hours (104). Even freezing plasma at — 20°C and at - 70°C did not activate factor VII. Both PT and APTT results were shown to be stable in plasma frozen at —20°C for 10 days and at -70°C for 21 days (104). 

Narayanan S. Preanalytical aspects of coagulation testing. Haematologica 1995 80(Suppl to No. 2), 1-5. 

Koepke J. A., Rogers, J., Allwier M. Pre-instrumental variables in coagulation testing. Am J Clin Pathol 1975 64,591-6. 

Nelson S., Pritt A., Marlar R. A. Rapid preparation of plasma for stat coagulation testing. Arch Pathol Lab Med 1994 118,175-6. 

Coagulation tests (aPTT, PT, INR) should be performed prior to initiating therapy to establish the patient s baseline values and guide later anticoagulation. 

Experimental measurements in each lake included particle concentration and size measurements in the water column, sedimentation fluxes in sediment traps, and chemical and size characteristics of materials recovered from sediment traps. The colloidal stability of the particles in the lake waters was determined with laboratory coagulation tests. Colloidal stability was described by the stability ratio (a). For a perfectly stable suspension, a = 0 for a complete unstable one, a = 1.)... 

Adjust dosage according to coagulation test results prior to each injection. Dosage is adequate when WBCT is approximately 2.5 to 3 times control value, or when aPTT is 1.5 to 2 times normal. 

Converting to oral anticoagulant therapy Perform baseline coagulation tests to determine prothrombin activity when heparin activity is too low to affect PT or INR. When the results of the initial prothrombin determinations are known, initiate the oral anticoagulant in the usual amount. Thereafter, perform coagulation tests and prothrombin activity at appropriate intervals. When the prothrombin activity reaches the desired therapeutic range, discontinue heparin and continue oral anticoagulants. 

Hypersensitivity to heparin severe thrombocytopenia uncontrolled bleeding (except when it is due to DIG) any patient for whom suitable blood coagulation tests cannot be performed at the appropriate intervals (there is usually no need to monitor coagulation parameters in patients receiving low-dose heparin). 

Bleeding abnormalities Ticarcillin or piperacillin may induce hemorrhagic manifestations associated with abnormalities of coagulation tests. 

Prior to initiation of therapy coagulation tests, hematocrit, platelet count... 

Activated clotting time, aPTT, BP, cardiac function, and other coagulation tests... 

The pathogenesis of the hypercoagulable state in nephrotic syndrome is complex because plasma levels of both fibrinolytic and regulatory proteins may be altered. Routine coagulation tests (Quick test and activated partial thromboplastin... 

Minimum Heparin in a Lacquer. Earlier work (3) using coagulation tests in cones showed that the anticoagulant effect of a lacquer containing heparin-benzalkonium compound (GBH) depended not only on the total amount of heparin in the lacquer, but also required a minimum concentration. Variation of heparin content at constant film thickness (5 microns) indicates a critical level between 0.3 and 0.5 fig./cm.2 variation of film thickness at 0.3 or 0.6% BH in the film indicates a similar critical level,... 

Earlier data (3) obtained with tests in cones and chemical determination suggested that the anticoagulant effect of heparin introduced on the wall was greater than that to be expected if all the heparin were dissolved in the plasma. This conclusion requires checking with more uniform heparin layers and improved coagulation test techniques on flat surfaces. It is known that some heparin goes into solution in plasma from GBH or PVPyrH surfaces, as prepared by us, and it seems probable that this is generally true for any adsorbed heparin system in which the... 

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