Common Collection Errors | AutoCyte Prep | Biopsy Tissue | Blood Cultures | Coagulation | CSF | Cytogenetics | Cytopathology | Fecal | Pap Smears | Throat Culture | Urine Collection | Viral | Wound Sample
Avoiding Common Collection Errors
attention to routine procedures can eliminate most of the errors outlined in
this section. 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 ensure a sufficient quantity of
each type of specimen indicated for the procedures to be performed, please
consult the volume requirements published in the LSG.
the common errors affecting all types of specimens include:
Failure to label a specimen correctly and to provide all pertinent
information required on the test request form. (See
Blood Chemistry and
Hematology - Blood Collection/Transport Containers.)
Insufficient quantity of specimen to run test or QNS (quantity not
Failure to use the correct container/tube for appropriate specimen
Inaccurate and incomplete patient instructions prior to collection.
Failure to tighten specimen container lids, resulting in leakage and/or
contamination of specimens.
common serum preparation errors include:
Failure to separate serum from red cells within 60 minutes of venipuncture.
Failure to allow the specimens to clot before centrifugation. (See
on clotting and serum-separator tubes and red-stopper tubes.)
Hemolysis: red blood cells break down and components spill into serum.
Causes and prevention are discussed under the section on hemolysis.
Lipemia: cloudy or milky serum sometimes due to the patient's diet
(discussed under the section on lipemia).
common errors in the preparation of plasma include:
Failure to collect specimen in correct additive.
Failure to mix specimen with additive immediately after collection.
Hemolysis or damage to red blood cells breakdown.
Incomplete filling of the tube, thereby creating a dilution factor excessive
for total specimen volume (QNS).
Failure to separate plasma from cells within 30-45 minutes of venipuncture
for those specimens requiring this step.
Failure to label transport tubes as "plasma".
Failure to indicate type of anticoagulant (eg, "EDTA", "citrate", etc.
common urine collection errors include:
Failure to obtain a clean-catch, midstream specimen.
Failure to refrigerate specimen or store in a cool place.
Failure to provide a complete 24-hour collection/aliquot or other timed
Failure to add the proper preservative to the urine collection container
prior to collection of the specimen.
Failure to provide a sterile collection container and to refrigerate
specimen when bacteriological examination of the specimen is required.
Failure to tighten specimen container lids, resulting in leakage of
Failure to provide patients with adequate instructions for 24-hour urine
Failure to divide specimen into separate containers for tests with such
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
Grossly hemolyzed samples will be rejected. A sample visibly
hemolyzed will be rejected for the following analytes:
Acid Phosphatase, Alkaline Phosphatase Isoenzymes, Alkaline Phosphatase,
Amylase, Amylase Isoenzymes, ALT, AST, Bilirubin, CK Isoenzymes, CK-MB, CPK
Folate, Glucose, Lipase, LDH, LDH Isoenzymes, Phosphorous, Potassium, RPR, Type
and Crossmatch, Type and Screen, VDRL(CSF), Alpha-fetoprotein.
Hemolysis can be caused by:
mixing additive tubes too vigorously or using rough handling during
drawing blood from a vein that has a hematoma
pulling back the plunger on a syringe too quickly
using a needle with too small of a bore for the venipuncture
using too large a tube when using a small diameter butterfly needle
frothing of the blood caused by improper fit of the needle on a syringe.
forcing the blood from a syringe into an evacuated tube
the tourniquet on for longer than one minute
Most cases of hemolysis can be avoided by observing the steps listed.
For routine collections, use a 20- to 22-gauge needle. (On occasion,
however, it may be necessary to use a 23-gauge needle for patients from
elderly and pediatric populations with small or difficult veins.)
If there is air leakage around the needle or loss of vacuum in the tube,
replace the vacuum tube.
If you are using your own collection equipment instead of the vacuum tube
technique, use only clean, dry, sterile needles, syringes, and tubes.
Collect blood in room temperature containers unless the specimen requirement
When there is difficulty accessing a vein or when a vacuum tube fills too
slowly due to a difficult venipuncture, damage to the red blood cells may
result. Correct by collecting a fresh tube when blood flow is established or
select another puncture site and, using sterile/unused equipment, collect a
second specimen. Also, a blood pressure cuff will reduce trauma to fragile
red blood cells.
Do not remove the needle from the vein with the vacuum tube engaged. This
applies to both the last tube collected during a routine venipuncture and to
tubes collected during a difficult procedure.
Premature removal of the tube causes a rush of air to enter the tube, which
may result in damage to the red cells.
Be as gentle as possible, drawing the blood evenly. Too much pressure in
drawing blood into a syringe or forcefully ejecting blood into a collection
tube from a syringe may damage red cells.
Allow collection site to dry after cleaning. Alcohol used to clean the
puncture site may cause contamination in a tube.
Do not collect a specimen in a hematoma.
Allow specimen to clot completely before centrifuging.
Do not centrifuge the specimen for a prolonged period of time.
of Tubes with Anticoagulant
anticoagulants, preservatives, clot activators). When using vacuum tubes
containing an additive:
collection tubes with anticoagulant should be inverted gently as soon after
collection as possible to prevent clotting. All blood collection tubes must be
filled to the fill line in order to prevent dilution of blood components. Tubes
with anticoagulant improperly filled will be rejected.
the samples to the laboratory promptly. Valid measurement of analytes in serum
or plasma requires prompt separation from the blood cells and analysis in the
laboratory. When left unseparated, analytes shift between the cells and the
plasma or serum and glucose, is consumed. In addition, some analytes are
unstable at room temperature. Microbiology specimens require specific
preservation methods according to body site. Refer to specific test for details.
Tap the tube gently at a point just below the stopper to release any
additive adhering to the tube or stopper.
Permit the tube to fill completely to ensure the proper ratio of blood to
additive. There will be some dead space at the top of the tube.
To ensure adequate mixing of blood with the anticoagulant or preservative,
use a slow rolling wrist motion to invert the tube gently five or six times.
Failure to invert tubes may lead to the formation of microscopic clots.
Rapid wrist motion or vigorous shaking may contribute to hemolysis.
Check to see that all the preservative or anticoagulant is dissolved. If any
preservative powder is visible, continue inverting the tube slowly until the
powder is dissolved.
If multiple samples are being drawn, invert each specimen as soon as it is
drawn. Do not delay. Place the tube upright in a rack as quickly as possible
Note: The serum-separator tube is an
additive tube and should be inverted five to six times after collection. Allow
the tube to stand 15-30 minutes for complete clotting to occur prior to
Vacuum Tubes without Anticoagulants
using vacuum tubes containing no additives:
Permit the tube to fill completely.
Let the specimen stand for a minimum of 30 minutes and not longer than 60
minutes prior to centrifugation. (CLSI Guidelines recommends no more than 2
hours.) This allows time for the clot to form. If the specimen is allowed to
stand for longer than 60 minutes, chemical activity and degeneration of the
cells within the tube will take place, and test results may be altered.
Centrifuge the specimen at the end of the waiting period in strict
accordance with the manufacturer's instructions for speed and duration of
centrifugation (usually 10-15 minutes).
Inadequate mixing of the vacutainer tubes as soon as possible after the
phlebotomy will result in the blood not mixing with the anti-coagulant. By
gently inverting the vacutainer tube 4-10 times, the blood will mix and clotting
will not occur.
the most common and expensive errors 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 additional expense and inconvenience to the
patient and to the physician. To ensure an adequate specimen volume:
if 4 mL of serum are required, draw at least 10 mL whole blood. If there is
difficulty in performing venipuncture, minimum volume may be submitted if it is
indicated in the test description. For most profile testing, draw at least two
10-mL serum-separator tubes. If pediatric tubes are used, be sure to collect an
adequate volume of specimen to perform the test.
Provide patients with adequate containers and instructions for 24-hour urine
and stool collections.
most serum and plasma tests, check to be certain that the transport tube is
half full. Note: Certain tests (eg, prothrombin time) require a 90% to 100%
full tube in order to achieve the proper blood-to-anticoagulant ratio;
otherwise, the specimen may be found to be QNS.