Specimen Processing and Handling
Updated October 27, 2026
A perfect draw can still give a wrong result if the specimen is labeled, handled or processed badly. Processing is a domain of its own on the NHA CPT exam. Here’s what to know, followed by free practice questions. Always follow your laboratory’s procedure manual for times, temperatures and rejection rules.
Labeling
- Label tubes at the bedside, in front of the patient, right after collection. Never pre-label.
- Labels usually need the patient’s full name, a second identifier (such as date of birth or medical record number), the date and time of collection, and the collector’s initials.
- Identify every patient with at least two identifiers before collecting.
Clotting and centrifuging
- Serum tubes must clot fully before centrifuging; follow the tube manufacturer’s clotting time.
- Plasma tubes contain an anticoagulant and can be centrifuged right away.
- Balance the centrifuge with tubes of equal weight opposite each other, and keep the tubes capped.
- Don’t open the centrifuge until it has stopped completely.
Hemolysis: common causes
Hemolysis (broken red blood cells) can falsely raise potassium and other results. Common causes:
- Using a needle that is too small
- Shaking tubes instead of inverting them gently
- Drawing through wet alcohol
- Forcing blood through a syringe needle into a tube
- Squeezing hard during a capillary puncture
Why a specimen may be rejected
- Missing or wrong label, or a label that doesn’t match the requisition
- Wrong tube type for the test
- Clotted specimen in an anticoagulant tube
- Hemolysis that affects the test
- Underfilled tube, especially light blue tubes
- Wrong temperature or too long in transit
Free practice questions
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When should specimen tubes be labeled?Answer: BLabeling at the bedside right after collection, in front of the patient, prevents mix-ups. Pre-labeling tubes risks putting the wrong patient's blood in a labeled tube.
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How many patient identifiers should be checked before collection?Answer: AUse at least two identifiers, such as full name and date of birth. The room number isn't an acceptable identifier.
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Which practice is most likely to cause hemolysis?Answer: CShaking breaks red blood cells. Tubes should be inverted gently the number of times the manufacturer recommends.
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Before centrifuging, a serum tube must:Answer: DSerum tubes need to clot fully before centrifuging; otherwise fibrin can form in the serum and interfere with testing. Follow the tube manufacturer's clotting time.
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Why must a centrifuge be balanced?Answer: AAn unbalanced centrifuge can vibrate, damage the machine and break tubes, creating a hazard. Place tubes of equal weight opposite each other.
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A light blue tube for a coagulation test is only half full. What should usually happen?Answer: CLight blue tubes need the correct blood-to-citrate ratio. An underfilled tube gives inaccurate coagulation results, so the specimen is usually rejected and recollected.
Pass your phlebotomy exam on the first try
- All 173 questions on safety, patient preparation, routine and special collections and processing
- An explanation for every answer, with the CLSI standard, OSHA rule or guideline behind it
- Unlimited full 100-question practice exams, with each domain in its real share