5.3 Specimen Processing & Handling
Key Takeaways
- Every specimen must be labeled at the patient's side, before leaving the room, with at least two patient identifiers plus collection date, time, and the phlebotomist's ID; unlabeled or mislabeled specimens are the most common rejection cause.
- Most serum tubes need a 30-60 minute clot time before centrifugation, and specimens should generally be centrifuged once for the time and speed defined by the lab; re-spinning a gel tube is not recommended.
- Light-sensitive analytes (bilirubin, vitamin B12, folate) are protected from light, chilled specimens (lactic acid, ammonia, blood gases) go on ice, and 37 C specimens (cold agglutinins, cryoglobulins) are kept warm in transit.
- Aliquots must be labeled to match the parent specimen, and aliquoting from different patients is never done simultaneously to prevent mix-ups.
- Forensic and legal specimens require a documented chain of custody: every transfer of the specimen is recorded with names, dates, times, and signatures from collection to testing.
Why Processing Matters
Processing and handling is roughly 14% of the NHA Certified Phlebotomy Technician (CPT) exam. A perfectly drawn specimen is worthless if it is mislabeled, transported wrong, or processed late. This domain is where pre-analytical errors are caught — or created.
Labeling Requirements
Labeling is the most heavily tested processing topic because mislabeled and unlabeled specimens are the #1 cause of specimen rejection.
When and What
Label the tube at the patient's side, immediately after collection, and before leaving the room. Never pre-label tubes before the draw and never label after leaving the patient. A complete label includes:
| Required label element | Example |
|---|---|
| Patient first and last name | Jane A. Doe |
| Second unique identifier | Date of birth or medical record number |
| Date of collection | 2026-05-17 |
| Time of collection | 0815 |
| Phlebotomist initials/ID | JP |
Match the label and requisition to the patient using the two-identifier rule (active confirmation with the patient when possible). A specimen labeled with only a name (no second identifier), the wrong patient, or no label is rejected and must be recollected.
Transport, Temperature, and Light Protection
Many analytes degrade between collection and testing. The phlebotomist controls three transport variables: time, temperature, and light.
| Handling need | Examples | Method |
|---|---|---|
| Chilled / on ice | Lactic acid, ammonia, arterial blood gas, gastrin | Transport in ice slurry immediately |
| Body temperature (37 C) | Cold agglutinins, cryoglobulins | Pre-warmed tube; keep warm in transit |
| Protect from light | Bilirubin, vitamin B12, folate, beta-carotene, porphyrins | Amber tube or foil wrap |
| Ambient, prompt | Most routine chemistry/hematology | Standard transport, deliver within time limit |
General rule: deliver specimens to the lab as soon as possible. Whole-blood specimens for many tests should reach the lab within 45-60 minutes so they can be processed within the recommended window.
Centrifugation
Centrifugation spins a tube at high speed to separate cells from serum or plasma.
Key Rules
- Clot first. Serum tubes (red, gold/SST) must fully clot — typically 30-60 minutes at room temperature — before centrifuging. Centrifuging too early produces fibrin and a poor separation.
- Plasma tubes (e.g., PST lithium heparin) do not need a clot time and can be spun promptly after proper mixing.
- Balance the centrifuge. Place tubes of equal size and volume directly opposite each other. An unbalanced centrifuge can break tubes, aerosolize blood, and damage the rotor.
- Cap the tubes and close the lid; never open the lid while spinning, and let the rotor stop on its own.
- Spin once at the lab-defined time and speed. Re-centrifuging a gel-barrier tube is generally not recommended because it can release cellular contents into the serum.
Aliquoting
An aliquot is a portion of a specimen transferred into a separate labeled tube (for example, to run tests on multiple analyzers).
- Each aliquot tube must be labeled to exactly match the parent specimen identifiers.
- Process and aliquot one patient's specimen at a time — never have two patients' open tubes side by side, to prevent transfer errors.
- Use a transfer device; do not pour, which risks aerosols and contamination.
- Provide enough volume for the test plus instrument dead volume.
Time Constraints
Each test has a maximum interval from collection to processing/testing. Common exam-relevant limits:
| Specimen | Typical limit |
|---|---|
| Serum/plasma separated from cells | Within ~2 hours of collection |
| Routine coagulation (PT/INR) | Tested within ~24 hours (citrate) |
| aPTT | Tested within ~4 hours |
| EDTA smear for morphology | Made within ~1 hour |
| Glucose (no inhibitor tube) | Separate quickly; glycolysis lowers glucose ~5-7%/hr |
When a limit is exceeded, the specimen may be rejected and recollected.
Specimen Rejection and Recollection Criteria
A specimen is rejected when its integrity is compromised enough to produce unreliable results. Common rejection reasons:
- Unlabeled or mislabeled (no second identifier, wrong patient) — most common.
- Hemolyzed — falsely raises potassium, LDH, and other analytes.
- Clotted anticoagulated specimen (e.g., a clotted EDTA CBC) — absolute rejection.
- Quantity not sufficient (QNS) — too little blood, especially wrong blood-to-additive ratio in citrate tubes.
- Wrong tube/additive for the test ordered.
- Improper handling — not chilled/warmed/protected, or delivered past the time limit.
- Contaminated (e.g., drawn above an IV, diluted).
When a specimen is rejected, document the reason, notify the appropriate staff, and recollect when possible rather than reporting questionable results.
Chain of Custody
For forensic and legal specimens (blood alcohol, court-ordered drug screens, employment testing), a chain of custody is a documented record proving the specimen was controlled and identified from collection through testing.
| Chain-of-custody element | What is recorded |
|---|---|
| Collector identification | Who drew the specimen |
| Patient/donor identification | Verified ID, sometimes a witness |
| Date and time | Exact collection time |
| Tamper-evident seal | Specimen sealed in front of donor |
| Transfer log | Every person who handled it, with signatures, dates, and times |
Any break in the documented chain can make the result inadmissible. Follow facility and legal protocol exactly, use the required non-alcohol prep for blood alcohol, and never leave a forensic specimen unsecured.
When should a blood specimen be labeled?
A serum separator (SST/gold-top) tube should be centrifuged only after:
Which specimen handling requirement is correctly matched?
A documented chain of custody is required primarily for which type of specimen?