Strict adherence to all stages of collection and processing is essential for accurate test results. Obtain plasma samples using Vacutainer tubes containing anticoagulant. These specimens can be centrifuged within minutes of collection. Any vacuum tubes containing anticoagulants should be gently inverted 8-10 times immediately after blood collection to ensure the intended effect of the additive.
When the blood clots, a serum sample is taken from the test tube. Before centrifugation, the sample must be completely solidified.
Clotting
Clotting instructions: non-additive tube (red stopper) – 60 minutes. SST tube – 30 minutes.
Recommended times are based upon an intact clotting process. Patients with abnormal Clotting due to disease, or those receiving anticoagulant therapy require more time for complete Clot formation. Separation of serum or plasma from cells should take place within 2 hours of collection to prevent erroneous test results.
When samples require freezing (2-8°C), samples should be immediately placed in small plastic tube bags, tied and placed in crushed ice or an ice-water mixture. Examples of samples that require freezing include ammonia and lactic acid.
How to centrifuge blood sample ?
Blood samples should be fully clotted before centrifugation. They should be centrifuged with the stopper in place. The recommended centrifugation time is 15 minutes at 3,000 rpm.
All samples collected in tubes with gel barriers should be properly centrifuged prior to shipping.
When storing the gel tubes after centrifugation, the serum/plasma is separated from the cells by the gel barrier. Physical separation of serum/plasma in contact with cells is recommended as soon as possible, up to 2 hours from the date of collection. After proper centrifugation, serum can be in contact with the gel barrier of SST tubes for up to 5 days and stored appropriately.
The centrifuge must be properly balanced. This is to prevent excessive vibration and potential breakage of the sample tube and is also necessary for proper separation of serum/plasma from cells.
Centrifuge Safety
Under normal operation, the centrifuge does not present any safety hazard. It is important to follow the safety precautions listed when operating the centrifuge:
Load Balancing: The centrifuge must be balanced before running. When centrifuging single or multiple tubes, each tube must be equilibrated with a tube of blood or a tube filled with water. so that the tube directly matches the tube opposite the centrifuge head. Never spin a single tube without a balance tube installed. Excessive noise or vibration indicates an unbalanced centrifuge.
Lid: Never open the lid while the rotor is moving. If the centrifuge has a safety interlock switch, do not tamper with this safety mechanism. If the switch is broken, do not operate the instrument until the switch has been repaired.
Biohazard: If the tube spills or breaks, there is a potential biohazard and the instrument must be cleaned using an approved cleaning procedure.
Specimen Storage
Any sample that must be stored for more than 1 hour prior to extraction should be refrigerated unless otherwise stated in the sample requirements. Do not refrigerate unspun potassium.
Any specimen that needs to be frozen should be frozen as soon as possible after collection. Always freeze specimens in plastic vials. Do not use glass.
Verify that the sample is correctly rotated, correctly labeled, and attached to the application. Place the appropriate specimen and application in the specimen transport bag.