Citrate Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Citrate and links to relevant pages within the course.
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|Preanalytic Variable Leading to False Thrombocytopenia|
The platelet count is only as good as the sample collected. Blood samples that are collected in EDTA or sodium citrate tubes for coagulation purposes should be inverted 5 - 10 times for proper mixing of the anticoagulant and the blood. If the tube is not mixed, small fibrin clots may form, causing a falsely decreased platelet count.
|Pseudo-thrombocytopenia: Platelet Satellitism and Platelet Clumping|
Platelet satellitism and platelet clumping can cause pseudo-thrombocytopenia. Platelet satellitism was first reported in the early 1960's. It is a rare condition that occurs when an IgG antibody forms in the presence of EDTA, the anticoagulant that is used for the collection of hematology blood specimens. The IgG antibody is directed against the glycoprotein IIb/IIIa complex on the platelet membrane. As the antibody coats the platelets, the platelets rosette around segmented neutrophils, bands, and sometimes around monocytes. Antibody-coated platelets that are huddled around white blood cells (WBCs) will not be counted as platelets by automated equipment and the platelet count will be falsely decreased. If a peripheral blood smear is reviewed, platelets will be observed attached to WBCs. The image on the right illustrates platelet satellitism with platelets adhering to a neutrophil. Platelet clumping can also occur in the presence of EDTA and the platelet count again will be falsely decreased. The count will probably be flagged by the analyzer for platelet clumps or giant platelets. If either platelet satellitism or platelet clumping is observed on the peripheral smear, the sample could be recollected using sodium citrate as the anticoagulant. Platelets can then be counted using the automated method. The platelet count from a tube that contains liquid sodium citrate will need to be corrected for the dilutional effect of the citrate. This can be accomplished by multiplying the platelet count that is obtained from the automated analyzer by 1.1.
|The reactions seen in the portion of the API strip shown in the photograph, effectively rules out Escherichia coli.||View Page|
|Match collection tube colors and additive type on the right with clinical usage on the left.||View Page|
|Which of the following additives should be used for the collection of a sample for blood gas analysis:||View Page|
|Which of the following blood additives is most useful for serum collection:||View Page|
|Mixing Study: Specimen Requirements|
The specimen drawn for a mixing study must meet the following conditions for accurate testing: A properly filled 3.2% sodium citrate tube must be collected. Proper centrifugation to create platelet-poor plasma for analysis must occur; the presence of platelet phospholipids can interfere with the mixing study if an anti-phospholipid antibody is present. Testing must be performed within 4 hours of collection.
|Collecting Blood Specimens for Coagulation Testing|
Venous blood specimens for coagulation assays should be collected into a tube containing 3.2% buffered sodium citrate tube (blue top tube), yielding a whole blood sample with a 9:1 blood to anticoagulant ratio. Inadequate filling of the collection tube will decrease this ratio, and may affect test results.A blue top tube used for coagulation testing should be drawn before any other tubes containing additives. This includes tubes containing other anticoagulants and/or plastic serum tubes containing clot activators. A serum tube that does not contain an additive can be collected before the blue top tube.If a winged blood collection set is used in drawing a specimen for coagulation testing, a discard tube should be drawn first. The discard tube must be used to fill the blood collection tubing dead space to assure that the proper anticoagulant/blood ratio is maintained, but the discard tube does not need to be completely filled. The discard tube should be a nonadditive or a coagulation tube.If a blood specimen used for coagulation testing must be collected from an indwelling line that may contain heparin, the line should be flushed with 5 mL of saline, and the first 5 mL of blood, or 6 times the line volume (dead space volume of the catheter), be drawn off and discarded before the coagulation tube is filled.
|Which of the following statements is NOT correct?||View Page|
|Specimen Collection and Handling|
Some global specimen collection and handling issues to consider include:Specimens that contain nucleated cells will be of interest in DNA methodologies while specimens lacking nucleated cells are more useful in RNA methodologies.rRNA is more stable than mRNA, which is labile and sensitive to contamination.DNA is relatively stable and can be obtained from nonviable sources.Serum or plasma obtained by standard routine venipuncture procedures can be used as long as proper site selection and decontamination occur.Standard anticoagulants such as ethylenediaminetetraacetic acid (EDTA) and acid citrate dextrose (ACD) can be used; however, avoid the use of heparin as an anticoagulant as it interferes with some polymerase chain reaction (PCR) methodologies.When using fluorescence, fasting serum or whole blood specimens should be used to decrease the interference by lipids.
|When collecting blood samples, one anticoagulant to avoid, especially when performing PCR is:||View Page|
|Choose the anticoagulant most commonly used for hemostasis testing:||View Page|
|Yellow top tubes|
Contain either acid citrate dextrose (ACD), which maintains RBC viability and may be used for HLA phenotyping, DNA, paternity testing, or lymphocyte surface markers, or:
Sodium polyanetholesulfonate (SPS) which is sometimes used to collect blood culture specimens.
|Light blue top tubes|
These tubes contain the anticoagulant sodium citrate.
They are used mostly for coagulation (clotting) studies.
They must be completely filled to assure proper ratio of anticoagulant to blood.They must be inverted immediately after filling to prevent clotting.
|Order of Draw|
Blood collection tubes must be filled in a specific order to avoid specimen contamination from the additive in the preceding tube. The following order of draw is an accepted laboratory standard. 1. Tubes or bottles for blood cultures 2. Light-blue top tubes (sodium citrate) 3. Serum tubes (with or without clot activator) 4. Green top tubes (sodium or lithium heparin) 5. Lavender or pink top tubes (Potassium EDTA) 6. Gray (Sodium fluoride and sodium or potassium oxalate)
|Blood Collection Tubes|
Most blood collection tubes contain an additive that either accelerates clotting of the blood (clot activator) or prevents the blood from clotting (anticoagulant). A tube that contains a clot activator will produce a serum sample when the blood is separated by centrifugation and a tube that contains an anticoagulant will produce a plasma sample after centrifugation. Some tests require the use of serum, some require plasma, and other tests require anticoagulated whole blood. The table below lists the most commonly used blood collection tubes.Tube cap colorAdditiveFunction of AdditiveCommon laboratory testsLight-blue3.2% Sodium citratePrevents blood from clotting by binding calciumCoagulationRed or gold (mottled or "tiger" top used with some tubes is not shown)Serum tube with or without clot activator or gelClot activator promotes blood clotting with glass or silica particles. Gel separates serum from cells.Chemistry, serology, immunologyGreenSodium or lithium heparin with or without gelPrevents clotting by inhibiting thrombin and thromboplastinStat and routine chemistryLavender or pinkPotassium EDTAPrevents clotting by binding calciumHematology and blood bank GraySodium fluoride, and sodium or potassium oxalateFluoride inhibits glycolysis, and oxalate prevents clotting by precipitating calcium.Glucose (especially when testing will be delayed), blood alcohol, lactic acid
|A blood collection tube that has a light-blue top contains which of these anticoagulants?||View Page|
|Procedure for Using a Winged Blood Collection Device to Collect a Specimen for Coagulation Tests|
A light-blue top tube (a blood collection tube containing 3.2% sodium citrate) that will be used for coagulation testing must be filled to completion. Under-filling the tube changes the ratio of blood to anticoagulant. This can affect the accuracy of coagulation tests that are performed using this specimen. If a winged blood collection device (butterfly) is used to collect a light-blue top tube for coagulation studies, a waste tube should be drawn first, if the coagulation tube is the first tube to be collected for patient testing. The waste tube must also be a light-blue top tube or a tube that contains no additives. This waste tube is drawn first to remove the air in the tubing of the winged collection device. Once blood flows through the tubing, the waste tube can be removed and discarded. The waste tube does not need to be completely filled. If the air is not displaced from the tubing into a waste tube, it will be drawn into the tube used for testing and cause a short-fill of the tube. Less volume of blood in the tube alters the required blood to anticoagulant ratio needed for coagulation studies.
|Categories of Transfusion Reactions|
Adverse complications of transfusions can be classified into several categories:Immune-mediated transfusion reactions are those that trigger a response from the patient's immune system. Many transfusion reactions are mediated by the recipient's immune system. These reactions occur as a result of antigen-antibody interactions. Antibodies involved include those with specificity towards antigens on red cells, white cells, or platelets. In general, the immune responses occur in three stages: The immune system detects foreign material (antigen)The immune system processes the antigenThe immune system mounts a response to remove the antigen from the bodyNon-immune mediated hemolytic transfusion reactions are caused by the physical or chemical destruction of transfused RBCs, bacterial contamination, circulatory overload, or citrate toxicity. Acute reactions are those that occur during or within 24 hours after the transfusion.There is usually a rapid onset of symptoms and these reactions may be fatal. Delayed reactions occur weeks or months after the transfusion of blood or blood components.
|Physical and Chemical Mechanisms of Hemolysis|
Patients can experience a transfusion reaction caused by a range of physical or chemical factors. These factors can either affect the blood component or result from a transfusion event. These reactions include physical red cell damage, depletion or dilution of coagulation factors and platelets, hypothermia, citrate toxicity, hypokalemia or hyperkalemia, and air embolism. Membrane damage and lysis can occur to red blood cells (RBCs) because of hypotonic or hypertonic solutions, heat damage from blood warmers, and mechanical damage caused by blood pumps. Platelets and coagulation factors may become depleted or diluted from a massive transfusion. Hypothermia, a core body temperature of less than 35°C, can occur from transfusions of large volumes of cold products. Hyperkalemia is caused by the intracellular loss of potassium from the red cells during storage. Hypokalemia may result from transfusion of potassium depleted cells such as washed RBCs. Signs and symptoms of physically or chemically induced reactions are non-specific. Some of the more common signs include: ChillsNumbnessNausea Vomiting Cardiac arrhythmiaAltered respiration Additional laboratory tests to investigate a reaction are electrolytes, blood pH, glucose, urinalysis, complete blood count (CBC), prothrombin time (PT) and activated partial thromboplastin time (aPTT). Treatment involves correcting the underlying cause of the symptoms. For example, a patient with hypothermia may be given a heat blanket. Attention to proper transfusion practices will help prevent these types of reactions.