Laboratory tests contribute vital information about a patient's health. Correct diagnostic and therapeutic decisions rely, in part, on the accuracy of test results. Adequate patient preparation, specimen collection, and specimen handling are essential prerequisites for accurate test results. The accuracy of test results is dependent on the integrity of specimens. Show
Safety and Disposal Considerations in Specimen CollectionIn all settings in which specimens are collected and prepared for testing, laboratory and health care personnel should follow current recommended sterile techniques, including precautions regarding the use of needles and other sterile equipment. Treat all biological material as material that is potentially hazardous as well as contaminated specimen collection supplies. For all those who are involved in specimen collection and preparation, the responsibility to adhere to current recommendations designed to maintain the safety of both patients and health care workers does not end when the patient is dismissed. There are four steps involved in obtaining a good quality specimen for testing: (1) preparation of the patient, (2) collection of the specimen, (3) processing the specimen, and (4) storing and/or transporting the specimen. Since information related to any of these areas may change as clinical laboratory technology changes, please refer to the latest edition of the Labcorp Directory of Services and Interpretive Guide for current instructions. PreparationPrior to each collection, review the appropriate test description, including the specimen type indicated, the volume, the procedure, the collection materials, patient preparation, and storage and handling instructions. Preparing the Patient. Provide the patient, in advance, with appropriate collection instructions and information on fasting, diet, and medication restrictions when indicated for the specific test. Preparing the Specimen. Verify the patient's identification. Proper identification of specimens is extremely important. All primary specimen containers must be labeled with at least two identifiers at the time of collection. Submitted slides may be labeled with a single identifier, but two identifiers are preferred. Examples of acceptable identifiers include (but are not limited to): patient's name (patient's first and last name exactly as they appear on the test request form), date of birth, hospital number, test request form number, accession number, or unique random number. A location such as a hospital room number is not an appropriate patient identifier. If chain of custody documentation is necessary for the procedure, follow the appropriate protocol. All specimens should be labeled in the presence of the patient. Process and store the specimen(s) as required. Appropriate storage and handling are necessary to maintain the integrity of the specimen and, consequently, the test results. Avoiding Common ProblemsCareful attention to routine procedures can eliminate most of the potential problems related to specimen collection. Materials provided by the laboratory for specimen collection can maintain the quality of the specimen only when they are used in strict accordance with the instructions provided. To collect a sufficient quantity of each type of specimen indicated for the procedures to be performed, please consult the volume requirements published in this Directory. General Specimen Collection. Some of the common considerations affecting all types of specimens:
Serum Preparation. The most common serum preparation considerations:
Plasma Preparation. The most common considerations in the preparation of plasma:
Urine Collection. The most common urine collection considerations:
Collection ProceduresCollection of Vacuum Tubes Containing Additives (eg, anticoagulants, preservatives, clot activators, gel-barrier). When using vacuum tubes containing an additive:
Collection of Vacuum Tubes Without Anticoagulants. When using vacuum tubes containing no additives:
HemolysisIn general, grossly or even moderately hemolyzed blood specimens may not be acceptable for testing. Hemolysis occurs when the red cells rupture and hemoglobin and other intracellular components spill into the serum. Hemolyzed serum or plasma is pink or red, rather than the normal clear straw or pale yellow color. Most cases of hemolysis can be avoided by observing the steps listed.
Lipemic Serum or Plasma (Turbidity)Normal serum or plasma is a clear and light yellow to straw in color. Turbid serum or plasma appears cloudy or milky. Serum or plasma may be cloudy due to bacterial contamination or chronic or transient high lipid levels in the patient's blood. The primary dietary sources of lipids (fatty substances) are meats, butter, cream, and cheese. Patients who consume these foods within the 24-hour period immediately preceding collection of a blood specimen may have temporarily elevated lipid levels, which may be manifested by cloudy or lipemic serum. Lipemic serum or plasma may not be a true indicator of the patient's physiologic state. (See Figure 1.) Regardless of diet and length of fast, some patients may produce cloudy specimens. To avoid dietary-induced high lipid levels prior to testing, many physicians require patients to exclude the high-fat foods from their diets or to fast for 12 to 14 hours prior to specimen collection. For morning specimen collection, the laboratory recommends that the patient be required to fast from 6 PM on the previous evening. Quantity Not SufficientOne of the most common problems in specimen collection is the submission of an insufficient volume of specimen for testing. The laboratory sends out a report marked QNS (quantity not sufficient), and the patient has to be called back for a repeat collection at an inconvenience to the patient and to the physician. To ensure an adequate specimen volume:
Specimen Storage and Shipping TemperaturesThe definition of specimen temperatures for storage and shipping is as listed below: Room Temperature: 10.1 – 40.0 oC Refrigerated: 1.0 to 10.0 oC Frozen: -1.0 to -80.0 oC Outdoor Specimen LockboxesFor clients whose specimen lockboxes must be placed outdoors, adding a frozen gel pack to the lockbox during warmer weather will help provide a moderate temperature inside the lockbox until specimens are collected by your LabCorp service representative. Labcorp also offers a different lockbox for use at locations that experience “extreme” temperatures. Contact your local representative for more information. Refrigerant Bottles should be prepared for use by placing them in a freezer for four hours or longer. They should be frozen solid prior to being placed in the lockbox, and they should be frozen solid before each use, even though they may be used with specimens that are not frozen.
If it is not possible to avoid placing the specimen lockbox in direct sunlight, add 20°F to the temperatures listed above to determine how many frozen gel packs to use. For lockbox instructions and Q&A, select Instructions for Use. If a specimen that is frozen needs to be put into the lockbox, the Frozen Specimen Keeper can be used maintain that frozen state. Instructions for Use. Preparing the PatientPatient InstructionsIt is important to gain the patient's understanding and cooperation in obtaining an acceptable specimen. Patient StatesBasal State. In general, specimens for determining the concentration of body constituents should be collected when the patient is in a basal state (ie, in the early morning after awakening and about 12 to 14 hours after the last ingestion of food). Reference intervals are most frequently based on specimens from this collection period. The composition of blood is altered after meals by nutrients being absorbed into the bloodstream. Consequently, postprandial blood (blood drawn after a meal) is not suitable for some chemistry tests. An overnight fast is preferable (from 6 PM of the evening previous to collection) to ensure that the patient is in the basal state. This minimizes the effects of ingested substances on the test results. Before you collect the specimen, ask the patient when he/she last ate or drank anything. If the patient has eaten recently and the physician wants the test to be performed anyway, you should indicate “nonfasting” on the test request form. In the clinical information/comments section of the test request form, indicate the time the patient ate. Fasting does not include abstaining from coffee, tea, or sugar-free liquids. Fasting or diet restrictions, such as low-fat diets, should be explained in detail, particularly to aged or overanxious patients or their caregivers. Inform patients that fasting does not include abstaining from water. Dehydration resulting from water abstinence can alter test results. When specimens are not collected in the basal state, the following additional effects should be considered when interpreting test results.
Note: For chemistry profiles, 12- to 14-hour fasting specimens are recommended. Timed SpecimensThere are two types of timed blood specimens: One is for a single blood specimen ordered to be drawn at a specific time. The other is for a test that may require multiple blood specimens to be collected at several specific times. Single Specimens. Here are some instances in which timed single specimens may be required.
Multiple Specimens. Here are some instances in which timed multiple specimen tests may be ordered
Sequential SamplingDiagnosis of many endocrine diseases requires sequential sampling of blood and/or urine. Labcorp sometimes offers reduced fees for serial tests when the following conditions are met:
Serial MonitoringMonitoring a patient over time for a specific condition is a variation of sequential sampling. Many tumor markers (tests used to follow the patient's response to treatment for cancer) may be monitored over the course of several years. Specific instructions for serial monitoring are found in the test description for the applicable test being monitored. Interference of Medications and Other SubstancesMany common prescription and nonprescription (over-the-counter) medications can interfere with chemical determinations or alter levels of substances measured. Drug interference is complicated and often method-dependent such that only general recommendations can be stated here. Precautions to be observed must be determined by the physician, and the patient must then be told to avoid specified medications for the necessary periods of time prior to specimen collection. If the patient cannot be taken off the medication in question, its presence should be noted on the test request form. Summary: Interference of Medications and Other Substances
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