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Specimen Handling and Processing

What happens to the tube between the patient's arm and the analyzer decides whether the result is usable. This chapter covers labeling, mixing, transport conditions, time limits, centrifugation, and the defects that force a lab to reject a specimen.

Labeling with two identifiers

A correctly drawn specimen with a wrong label is more dangerous than no specimen at all, because the result will be believed and acted on. Labeling requires two patient-specific identifiers that stay with the person, matched against the requisition and, for inpatients, against the wristband. The physical location of the patient never counts as an identifier.

Two identifiers, both patient specific
Use the patient's full name plus a second identifier such as date of birth or medical record number. Room number, bed number, and floor are location data, not identifiers, and may not be used.
The Joint Commission NPSG.01.01.01
What goes on the label
The label carries the patient's full name, the identification number, the date and time of collection, and the collector's initials or identification code.
CLSI GP33
Label after collection, at the patient
Tubes are labeled after the draw is complete and in the patient's presence, before leaving. Prelabeling risks putting a label on a tube that is never drawn or drawn from the wrong patient.
CLSI GP33
Blood bank labeling is stricter
Type and crossmatch specimens require the collector to verify identification at the bedside, label at the bedside, and often attach a dedicated blood bank armband; a discrepancy triggers automatic recollection.
AABB Standards for Blood Banks and Transfusion Services
Never correct a label by writing over it
If a label is wrong, the specimen is either recollected or corrected only through the laboratory's documented relabeling procedure by the person who drew it; altering a label without that process invalidates the specimen.
Label placement matters
Apply the label lengthwise along the tube so the technologist can still see the specimen level and the color of the serum or plasma through the tube wall.

Mixing, transport, and time limits

Additive tubes only work if the blood meets the additive right away, which is why inversion counts differ by tube type. Once collected, specimens are transported upright and delivered inside defined windows, because cells keep metabolizing in the tube. Most delays show up as chemistry shifts long before anything looks visibly wrong.

Invert gently, do not shake
Mix by slow, complete end-over-end inversions immediately after filling each tube; shaking causes hemolysis and foaming. Typical counts are 3 to 4 for citrate, 5 for serum separator tubes, and 8 to 10 for heparin, EDTA, and fluoride oxalate tubes.
CLSI GP41
Transport upright
Carry and rack tubes stopper up. Upright transport promotes complete clotting in serum tubes, reduces agitation-related hemolysis, and keeps blood off the stopper where it can be aerosolized on opening.
CLSI GP44
Separate serum or plasma within two hours
Cells and serum or plasma must be physically separated within two hours of collection for most analytes, because glucose falls and potassium, LDH, and phosphorus rise while cells sit in contact with the fluid.
CLSI GP44
Serum tubes need a full clot first
Allow plain and gel serum tubes to clot undisturbed for about 30 minutes at room temperature before centrifuging; spinning early produces fibrin strands that clog analyzer probes.
Common test windows
Blood cultures go to the incubator as soon as possible, EDTA specimens for CBC are stable roughly 24 hours refrigerated, aPTT specimens are run within about 4 hours, and PT specimens within about 24 hours at room temperature.
CLSI H21
Stat and timed specimens
Stat and timed collections such as glucose tolerance samples, therapeutic drug peaks and troughs, and blood cultures must record the actual collection time, because the result is interpreted against that clock.

Temperature and light: specimens that need special handling

A minority of analytes are destroyed by ordinary handling and require chilling, warming, or protection from light. These lists are short, finite, and heavily tested, so memorize them by category rather than trying to reason them out. Note also what must never be chilled, because cooling a routine specimen creates its own errors.

Chilled specimens
Transport in an ice and water slurry, not on solid ice cubes, for ammonia, lactic acid, arterial blood gases, gastrin, parathyroid hormone, homocysteine, and catecholamines; slurry gives even cooling without freezing the cells at the contact point.
CLSI GP44
Do not chill potassium or CBC
Cooling whole blood causes potassium to leak out of red cells and falsely elevates the result, and refrigeration distorts cell indices, so routine chemistry and hematology tubes stay at room temperature.
Light-protected specimens
Bilirubin, vitamin B12, folate, vitamin A, carotene, and porphyrins degrade with light exposure and are wrapped in foil or collected in amber tubes; neonatal bilirubin is the classic exam example.
CLSI GP44
Body-temperature specimens
Cold agglutinins, cryoglobulins, and cryofibrinogen must be kept at 37 degrees Celsius from collection through separation, using a prewarmed tube or heat block, because the target protein precipitates when it cools.
CLSI GP44
Frozen aliquots
Some send-out analytes require the plasma or serum to be separated and frozen; freeze the aliquot, never the original whole blood tube, since freezing whole blood hemolyzes it completely.
Temperature during transport
Courier and pneumatic tube transport must hold specimens within the range the test requires, and the receiving lab documents arrival condition; a specimen that arrived warm when it needed ice is a rejection.

Centrifugation and processing

Centrifugation separates cells from fluid using controlled speed and time, and doing it wrong is a common source of unusable specimens. The two operational rules are balance the load and never open a running rotor. The two analytical rules are complete the clot before spinning and never respin a gel tube.

Balance opposing positions
Place tubes of equal size and equal fill directly across from each other; an unbalanced rotor vibrates, hemolyzes specimens, damages the instrument, and can break tubes.
Standard spin
Most serum and plasma tubes are spun with the stoppers on for about 10 minutes at the relative centrifugal force specified by the tube manufacturer, commonly in the range of 1000 to 1300 g.
CLSI GP44
Never open a moving centrifuge
Let the rotor come to a complete stop on its own; braking or opening the lid early resuspends cells, and a tube that broke during the spin can aerosolize infectious material.
Do not respin a gel tube
Once the gel barrier has formed, respinning can trap analytes below the gel or drive cells through it, producing falsely altered chemistry results. Respin only per the laboratory procedure and never after the gel has set.
Aliquot with care
Transfer serum or plasma to a labeled aliquot tube carrying the same identifiers and specimen number as the parent tube, without disturbing the cell layer, and never pour serum from one patient's tube into another patient's container.
Handle stoppers safely
Open tubes behind a shield or with a stopper removal device and point the opening away from the face, because aerosol released on decapping is a documented exposure route.
OSHA 29 CFR 1910.1030

Hemolysis, other interferences, and rejection criteria

Hemolysis is the most common preanalytical error in phlebotomy, and it is almost always caused by collection technique rather than by the patient. Recognize the pink-to-red serum, know which analytes it ruins, and know the technique errors that produce it. Rejection criteria are the lab's formal list of reasons a specimen cannot be tested.

What hemolysis does to results
Red cell rupture releases intracellular contents, so potassium, LDH, AST, magnesium, phosphorus, and iron read falsely high, while sodium is diluted downward and the red pigment interferes with bilirubin and other colorimetric methods.
Collection causes of hemolysis
Alcohol not allowed to dry, a needle finer than 23 gauge, vigorous shaking, forcing blood from a syringe through a needle into a tube, prolonged tourniquet time, milking a capillary site, and underfilled additive tubes all shear or lyse cells.
CLSI GP41
Lipemia and icterus
Lipemia is milky turbidity from recent fat intake or nonfasting collection and blocks optical readings; icterus is yellow-brown from high bilirubin. Both interfere with photometric assays and are noted at processing.
Clotted anticoagulant specimen
A clot in an EDTA or citrate tube means mixing was delayed or incomplete; the cell count and coagulation results are invalid and the specimen must be recollected, not filtered or shaken back into suspension.
Quantity not sufficient and short draws
A specimen below the volume the method requires is rejected as QNS. For citrate coagulation tubes any underfill is rejected outright because it changes the fixed nine-to-one ratio.
CLSI H21
Standard rejection list
Laboratories reject specimens that are unlabeled or mislabeled, in the wrong tube or preservative, hemolyzed, clotted, QNS, collected in an expired tube, leaking or contaminated, transported at the wrong temperature, or delivered past the analyte's stability limit.
CLSI GP44
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Last updated: July 2026

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