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Specimen Collection and Preparation Guidelines for Clinical Laboratories, Lecture notes of Clinical Medicine

Guidelines for collecting, preparing, and transporting specimens to ensure accurate test results in clinical laboratories. It covers different types of specimen containers, their uses, and preparation procedures for serum, whole blood, plasma, and coagulation studies. It also discusses common causes of unacceptable specimens, such as hemolysis, lipemia, and incorrect specimen type.

What you will learn

  • What are the common causes of unacceptable specimens and how can they be avoided?
  • How should serum, whole blood, and plasma be prepared for testing?
  • What are the different types of specimen containers and their uses?

Typology: Lecture notes

2021/2022

Uploaded on 09/27/2022

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Southeast Clinical Laboratories
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Specimen Collection Guidelines
The accuracy of any test result depends on the quality of the specimen submitted. Following the
collection, preparation and transport instructions will help to ensure the most accurate test results.
Specimen Collection Preparation
Prior to collecting the specimen, review the specimen requirements listed in the test listing section
of this manual. Note the proper specimen type to be collected, amount of sample necessary for
testing and special storage and/or transport instructions.
Each specimen container should be properly identified with the patient’s full name, date, time of
collection and specimen type. Each specimen must be accompanied by a properly completed test
requisition.
Specimen Collection Tubes (listed in recommended order of draw)
Red Top: Does not contain an anticoagulant. This tube is used for collecting serum or
clotted whole blood specimens. This tube should be used for all drug levels.
Serum Separator Tube (SST) (Tiger Top): Does not contain an anticoagulant but
contains a clot activator and serum separator gel. This tube is used for collecting serum.
Light Blue: Contains the anticoagulant sodium citrate. This tube is used for preparing
citrated plasma for coagulation studies. Tube should be inverted 8-10 times immediately
after collection to prevent clotting. It is also important to completely fill the tube to the
appropriate level since the ratio of blood to anticoagulant is critical for coagulation tests.
Green (Sodium or Lithium Heparin): Contains the anticoagulant sodium heparin or
lithium heparin. This tube is used for preparing heparinized plasma, whole blood, or bone
marrow specimens. Tube should be inverted 8-10 times after collection to prevent clotting.
Lavender (EDTA): Contains the anticoagulant EDTA. This tube is used for preparing
EDTA plasma, whole blood, or bone marrow specimens. Tube should be inverted 8-10
times after collection to prevent clotting.
Royal Blue: May contain either the anticoagulant EDTA or no anticoagulant. The tube
containing anticoagulant is used for preparing whole blood or plasma trace element
studies and the tube without anticoagulant is used for preparing serum trace element
studies.
Yellow: Contains the anticoagulant acid citrate dextrose (ACD). This tube is used for
preparing whole blood specimens used for special studies.
Gray: Contains the preservative sodium fluoride and the anticoagulant potassium oxalate.
This tube is used for preparing whole blood and plasma specimens such as glucose
testing or blood alcohol testing.
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Specimen Collection Guidelines

The accuracy of any test result depends on the quality of the specimen submitted. Following the collection, preparation and transport instructions will help to ensure the most accurate test results.

Specimen Collection Preparation

Prior to collecting the specimen, review the specimen requirements listed in the test listing section of this manual. Note the proper specimen type to be collected, amount of sample necessary for testing and special storage and/or transport instructions. Each specimen container should be properly identified with the patient’s full name, date, time of collection and specimen type. Each specimen must be accompanied by a properly completed test requisition.

Specimen Collection Tubes (listed in recommended order of draw)

Red Top: Does not contain an anticoagulant. This tube is used for collecting serum or clotted whole blood specimens. This tube should be used for all drug levels. Serum Separator Tube (SST) (Tiger Top): Does not contain an anticoagulant but contains a clot activator and serum separator gel. This tube is used for collecting serum. Light Blue: Contains the anticoagulant sodium citrate. This tube is used for preparing citrated plasma for coagulation studies. Tube should be inverted 8-10 times immediately after collection to prevent clotting. It is also important to completely fill the tube to the appropriate level since the ratio of blood to anticoagulant is critical for coagulation tests. Green (Sodium or Lithium Heparin): Contains the anticoagulant sodium heparin or lithium heparin. This tube is used for preparing heparinized plasma, whole blood, or bone marrow specimens. Tube should be inverted 8-10 times after collection to prevent clotting. Lavender (EDTA): Contains the anticoagulant EDTA. This tube is used for preparing EDTA plasma, whole blood, or bone marrow specimens. Tube should be inverted 8- 10 times after collection to prevent clotting. Royal Blue: May contain either the anticoagulant EDTA or no anticoagulant. The tube containing anticoagulant is used for preparing whole blood or plasma trace element studies and the tube without anticoagulant is used for preparing serum trace element studies. Yellow: Contains the anticoagulant acid citrate dextrose (ACD). This tube is used for preparing whole blood specimens used for special studies. Gray: Contains the preservative sodium fluoride and the anticoagulant potassium oxalate. This tube is used for preparing whole blood and plasma specimens such as glucose testing or blood alcohol testing.

Specimen Preparation Procedures

Serum: Collect whole blood in an amount 2 ½ times the required volume of serum so that a sufficient amount of serum can be obtained. To obtain serum, whole blood should be collected into either an SST or plain red top tube. After collection, allow the tube to sit in an upright position at room temperature for 30-45 minutes. After the clot has formed, centrifuge the tube for 10 minutes at 3400 rpm. Remove the tube and transfer the serum to a transport tube and store specimen as required. Whole Blood: Collect whole blood in the collection tube specified for the test. To avoid clotting, invert tube 8-10 times to mix the blood with the anticoagulant. Never freeze whole blood unless specifically instructed in the specimen requirements. Plasma: Collect blood in the collection tube specified for the test. Invert tube 8-10 times to ensure proper distribution of anticoagulant. Specimens collected in additive tubes for plasma may be centrifuged immediately. Centrifuge the tube for 10 minutes at 3400 rpm. Remove the tube carefully without disturbing the contents. Using a pipette, carefully transfer the plasma to a plastic tube taking care not to transfer any cellular material. Store the specimen as required. Coagulation/Hemostasis: To produce valid results for coagulation tests and factor assays, specimen integrity is crucial and must be maintained. All specimens sent for testing must be collected in the following manner:

  • Obtain venous blood by clean venipuncture. Avoid slow flowing draws and/or traumatic venipunctures as either of these may result in an activated or clotted specimen. Do not use needles smaller than 23 gauge. Do not leave the tourniquet on for an extended length of time before drawing the sample.
  • Draw a discard tube (plain red top), as a recommended procedure, before drawing coagulation specimens in light blue-top vacuum tubes (3.2% buffered sodium citrate). Discard the red top tube. Note: Reference intervals have been established using 3.2% buffered sodium citrate.
  • Fill light blue-top tubes as far as vacuum will allow and mix by gentle inversion. Exact ratio of nine parts blood to one part anticoagulant must be maintained. Inadequate filling of the sample tube will alter this ratio and may lead to inaccurate results. All coagulation specimens with time sensitive shipping requirements or delayed shipping must be processed in the following manner:
  • Centrifuge the specimen at 3400 rpm for 10 minutes. Hemolyzed specimens will be rejected.
  • Immediately remove only the top two-thirds of the platelet-poor plasma from the specimen using a plastic transfer pipet (use of glass transfer pipets may result in activation and/or clotting of the plasma). Place the plasma in a properly labeled transport tube and clearly mark the vial contents as PLASMA. Glass vials will be rejected.
  • Immediately freeze the plasma. Specimens must remain frozen during storage and shipment. A separate tube should be submitted for each assay requested.

Quantity Not Sufficient (QNS): QNS means that the specimen volume received for testing was not enough to meet the minimum volume required to perform the test at least once. The minimum specimen volume is the amount required to perform the test only once. Please refer to the test requirements for specimen volumes. Plasma Specimen Errors: Plasma contains fibrinogen and other clotting factors when separated from the red blood cells. The most common errors in the preparation of plasma include:

  • Failure to collect specimen in correct anticoagulant
  • Failure to mix specimen with anticoagulant immediately after collection
  • Incomplete filling of the tube, thereby creating a dilution factor excessive for total specimen volume
  • Improper centrifugation – Because platelets interfere with most coagulation tests, we must ensure that the plasma submitted for testing is platelet poor plasma. Urine Specimen Errors: Laboratory urine tests may require a random, 24-hour, or other timed collection. Please refer to the test information for type of sample and any special instructions that may need to be given to the patient.