Blood Specimen Handling & Testing Procedures PDF

Blood ammonia levels increase fast at room temperature because of in vitro amino acid breakdown. Therefore, a whole blood ammonia specimen must be placed in an ice slurry, quickly transported to the lab, separated from the cells, and quickly tested. A serum or plasma specimen should be centrifuged...

Blood ammonia levels increase fast at room temperature because of in vitro amino acid breakdown. Therefore, a whole blood ammonia specimen must be placed in an ice slurry, quickly transported to the lab, separated from the cells, and quickly tested. A serum or plasma specimen should be centrifuged within 2 hours of collection. Prolonged plasma/serum contact with the cells increases the possibility of altered analyte levels, intracellular changes, and hemolysis. Rimming the clot in a serum collection tube can cause contamination due to aerosols and hemolyze the specimen. It should be avoided. Freezing and thawing a blood specimen multiple times can hemolyze the red blood cells, affecting the lab results. Glucose is utilized by red blood cells even after blood collection. Therefore, the glucose levels will decline over time if left standing for extended periods of time. Glycolysis reduces serum glucose at a rate of 5% to 7% per hour (5-10 mg/dL) in normal uncentrifuged coagulated blood stored at room temperature. Therefore, the blood should be centrifuged and the cells and serum separated within two hours of collection to prevent changes in serum constituents. EDTA whole blood tubes that are used for hematology tests, such as CBCs, can safely be stored at room temperature for up to 24 hours without adversely affecting results. The specimen can then be refrigerated for up to 48 hours before testing. Longer storage may affect some CBC test results. Serum or plasma should not remain at room temperature (20-25°C) for a prolonged period of time, as this may adversely affect test results. If testing is not completed within eight hours, serum and plasma specimens should be refrigerated at 2-8°C, and if held longer than 48 hours, the plasma or serum specimen should be frozen at or below -20°C. Specimens that have been frozen should only be thawed once before testing in order to prevent possible deterioration of analytes and inaccurate patient test results. Vitamin B12, bilirubin (total and direct), beta carotene, and folate all break down in the presence of light. A light-sensitive specimen should be collected in a special amber-colored tube or, if such tube is not available, in a tube wrapped up in aluminum foil, 03C, PT, and creatinine are not affected by light. Hgb Mc, magnesium, and potassium are not affected by light. **Time** The specimen should not be delayed for more than two hours prior to centrifugation because some of the analyte levels (such as glucose, ionized calcium, bicarbonate, folate, etc.) may be falsely decreased due to cellular consumption or falsely increased (such as potassium, ALT, AST, creatinine, etc.) because they are released over time from cells into serum or plasma. Prolonged contact of serum with red blood cells can alter the results of some tests that use a serum sample. A potassium result could be significantly increased depending on the length of time that the serum remained **in** contact with the blood cells. The majority of potassium in the blood is contained within red cells. Continued contact with the red blood cells would allow potassium from the cells to leak into the serum portion. A gel barrier would prevent this contact, but if this type of tube is not used, the serum must be removed from the cells and transferred to another tube. The specimen can still be used and should not be discarded even though it was not collected into a gel barrier tube. It is crucial to the accuracy of the test that the serum is removed as soon as centrifugation is completed. Pneumatic tube system is a convenient transport medium used in healthcare facilities. When it comes to transporting laboratory specimens, special strict protocols are followed to ensure integrity of the specimen, safety of the operator, and to prevent contamination issues. According to CLSI guidelines, the tests negatively affected by pneumatic tube system transport are those influenced due to red cell disruption, such as potassium, plasma hemoglobin, acid phosphatase, and lactate dehydrogenase. CLSI states that the following tests are **NOT** affected by Pneumatic tube system transport: albumin, alkaline phosphatase, AST, chloride, creatinine, glucose, sodium, total bilirubin, total protein, BUN, uric acid, thrombin time, and WBC concentration. Specimen leakage should be prevented when transporting a urine specimen via the pneumatic tube system. At a minimum, a specimen must be in a primary receptacle that is leak-proof with a tightly secured lid or closure. The primary receptacle must then be placed into a secondary container, such as a zip-locked biohazard bag, to further protect against leakage of the specimen. If a specimen is sent through a pneumatic tube system, the integrity of the carrier into which the specimen is placed should be checked to prevent a mishap in the system during transport of the specimen. Look for cracks in the carrier and verify that the closure locks properly. The carrier should contain foam pads in order to provide cushioning and containment during transport. The container used to transport clinical laboratory specimens by courier has to have the appropriate label placed on it, which is the biohazard label or symbol. \"Biological Substance Category A\" or \"Biological Substance Category would be the appropriate labels for infectious substances that are shipped via air, highway, rail, or water using a commercial carrier. The specific label that is needed depends on the type of material that is being transported. The albumin test results will not be affected if the specimen is sent by the hospital\'s pneumatic tube system. The vibrations and shock to the blood specimen created during pneumatic tube transportation can damage the red blood cells and negatively affect some test results. CLSI recommends that potassium, plasma hemoglobin, acid phosphatase, and lactate dehydrogenase not be transported to the laboratory via pneumatic tube system. CLSI states that the following tests are **NOT** affected by Pneumatic tube system transport: albumin, alkaline phosphatase, AST, chloride, creatinine, glucose, sodium, total bilirubin, total protein, BUN, uric acid, thrombin time, and WBC concentration. A specimen without an additive or anticoagulant should be allowed to clot for at least 30 minutes prior to centrifugation. Incomplete clotting of the specimen will leave small fibrin residue in the serum, which would interfere with testing or clog the testing instrument probe or tubing. The specimen should not be held for more than two hours prior to centrifugation because some of the analyte levels (glucose) may be falsely decreased due to cellular consumption or falsely increased (potassium) due to hemolysis. Reduced centrifugation time and increased speed can leave residual separator gel particles in the serum, which can interfere with testing or clog the probes and the tubing of automated testing instruments. Improper balance of the centrifuge can result in potential tube breakage, exposure to biohazardous agents, and mechanical centrifuge damage. Compliance with standard procedures will avoid these effects. Reduced centrifugation time and increased speed can cause hemolysis which can interfere with accurate testing. It can also leave residual separator gel particles in the serum, which can interfere with testing or clog the probes and the tubing of automated testing instruments. Furthermore, it can cause incomplete separation of serum and cells, which will interfere with testing. Complete clotting is required for a serum specimen before centrifugation is started, otherwise, the fibrin residue may still be in the serum, which could interfere with testing. Plasma specimens contain anticoagulants and will not clot. It is recommended not to increase the centrifugation speed for a specimen because increased speed will cause the specimen to hemolyze. If there is a delay in centrifugation, the serum glucose levels may be decreased. The cells have to be separated from the serum because they will continue to consume the glucose present in the serum.