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newSchoolWorks.com › VoTechWorks › Health & Personal Services › Medical Assisting › Phlebotomy: Venipuncture, Capillary Collection, and Specimen Handling › Lesson 4
HLT-MEDI38-03 · Lesson 4 · 8.5 clock hours · theory

Pre-Analytical Variables: Patient Identification, Requisitions, and Specimen Integrity

Objective. Students explain how pre-analytical errors occur and correctly complete a specimen requisition and patient label using two patient identifiers, with zero critical errors.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed clinician in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it to make decisions about any patient or medication. Always follow your instructor, your supervising professional, and current official references and regulations.

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Why Pre-Analytical Errors Matter

The testing process is divided into three phases: pre-analytical, analytical, and post-analytical. The pre-analytical phase covers everything that happens before the specimen reaches the instrument — patient identification, requisition completion, collection, labeling, and transport. Research consistently shows that the majority of laboratory errors originate in the pre-analytical phase. Errors at this stage can cause incorrect test results, delayed diagnoses, wrong treatment, or serious patient harm — even death. As a medical assistant or phlebotomy technician, you control this phase entirely.

Patient Identification: The Two-Identifier Rule

Before collecting any specimen, you must confirm the patient's identity using two independent identifiers. Acceptable identifiers typically include:

Room number and bed number are never acceptable identifiers because they can change.

The correct protocol:

1. Ask the patient to state their full name and date of birth — do not read the information to them and ask them to confirm. Patients who are anxious, hard of hearing, or wish to please may confirm incorrect information.

2. Compare what the patient says against the requisition and, for inpatients, the wristband.

3. All three sources must match before you proceed.

If there is any discrepancy, stop the draw. Do not guess or assume. Notify the nurse or ordering provider and resolve the discrepancy through proper channels before collecting. Document what you did.

Completing the Specimen Requisition

A requisition is the written or electronic order that authorizes collection. It must contain:

If any required field is missing, contact the ordering provider or nursing staff to clarify before drawing. An incomplete requisition is a pre-analytical error in itself.

Labeling the Specimen Tube

Every tube must be labeled at the patient's side, immediately after collection, before you leave the room. Never prelabel tubes, and never label a tube away from the patient.

A complete specimen label includes:

A mislabeled or unlabeled tube must be recollected — relabeling a tube from memory is not acceptable and is considered a critical error.

Common Pre-Analytical Errors and Their Consequences

Wrong patient drawn: Collecting blood from the wrong patient is one of the most serious errors possible. It can result in a transfusion reaction if the specimen is used for blood typing, or incorrect medication decisions based on someone else's chemistry values.

Mislabeled tube: A tube bearing the wrong patient's name may lead to a completely different patient receiving a wrong diagnosis or treatment.

Hemolyzed specimen: Hemolysis (rupture of red blood cells) releases intracellular contents — especially potassium — into the serum or plasma. A hemolyzed potassium result can be falsely elevated and may cause a clinician to withhold necessary medication or administer treatment the patient does not need. Common causes include: using too small a needle with forceful aspiration, shaking tubes vigorously instead of gently inverting them, drawing from an IV line without following proper protocol, or allowing the specimen to sit too long before centrifuging.

Underfilled coagulation tube: Coagulation tests such as the PT/INR and aPTT require the correct ratio of blood to liquid anticoagulant (sodium citrate). If the tube is underfilled, the excess anticoagulant alters the clotting chemistry and produces falsely prolonged clotting times. A blue-top (sodium citrate) tube must be filled to the manufacturer's indicated fill line — typically within 10% of the stated volume.

Short draw or wrong order of draw: Drawing tubes in the wrong order can cause additive carryover between tubes, contaminating results. Always follow your facility's order-of-draw policy, which is based on Clinical and Laboratory Standards Institute (CLSI) guidelines.

Specimen Integrity During Transport

After collection, specimens must be handled correctly to remain valid:

Safety Summary

Every step in the pre-analytical phase is a patient safety checkpoint. If you are uncertain about the patient's identity, the requisition, or the specimen's condition — stop and verify. It is always safer to delay a draw than to proceed with doubt. Your initials on a label represent your professional accountability for that specimen.

Key terms8

Pre-analytical phaseThe stage of laboratory testing that occurs before the specimen is analyzed; includes patient identification, requisition review, collection, labeling, and transport — the phase where most laboratory errors originate.
Two-identifier ruleThe patient safety requirement to confirm identity using two independent pieces of information (such as full name and date of birth) before any specimen collection.
RequisitionA written or electronic order from a provider that authorizes specimen collection and specifies the tests to be performed; must be complete and accurate before collection begins.
HemolysisThe rupture or destruction of red blood cells, releasing their contents into the surrounding plasma or serum; a common pre-analytical error that can falsely alter test results, especially potassium.
Sodium citrate tube (blue top)A collection tube containing liquid sodium citrate anticoagulant used for coagulation testing; must be filled to the correct volume to maintain the proper blood-to-anticoagulant ratio.
Order of drawThe standardized sequence in which blood collection tubes must be filled to prevent additive carryover that could contaminate specimens and alter test results; based on CLSI guidelines.
Specimen integrityThe condition of a specimen that makes it suitable for accurate testing; compromised by hemolysis, incorrect fill volume, improper storage, or excessive time before analysis.
Additive carryoverContamination that occurs when trace amounts of an anticoagulant or additive from one tube are transferred into the next tube if tubes are drawn in the wrong order.
In class: Analyze five case studies of real-world pre-analytical errors (wrong patient, mislabeled tube, hemolyzed specimen, underfilled coagulation tube) and for each write the probable cause, the potential patient harm, and the corrective action. · Role-play patient identification using the two-identifier protocol: one student acts as the patient and gives intentionally incorrect information; the phlebotomist student must recognize the discrepancy and follow correct resolution steps before proceeding. · Complete five mock requisition forms and matching specimen labels provided by the instructor, then compare against an answer key and discuss any discrepancy under instructor guidance.
Materials: Sample physician requisition forms, blank specimen labels, simulated patient ID wristbands, case study handouts, phlebotomy textbook chapter on pre-analytical variables
Check: Students complete a final requisition and label exercise with five patient scenarios; all five must be completed with zero critical identifier errors (name, DOB, date, time, collector initials, test) to pass — any critical error requires a redo.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Phlebotomy: Patient Preparation and Identification
1. A phlebotomist approaches an inpatient bed and reads the patient's name from the wristband aloud, asking, 'Are you Maria Gonzalez?' The patient nods yes. What is wrong with this approach?
Phlebotomy: Specimen Collection and Handling
2. A blue-top sodium citrate tube is drawn for a PT/INR test but is only half full because the vein collapsed. What is the most likely effect on the test result?
Phlebotomy: Patient Preparation and Identification
3. Which of the following is an acceptable patient identifier when confirming identity before phlebotomy?
Phlebotomy: Specimen Collection and Handling
4. A phlebotomist collects three tubes and then walks to the nurses' station to label them using the requisition. This practice is:
Phlebotomy: Specimen Collection and Handling
5. A potassium result comes back at 6.8 mEq/L on a patient who had a normal potassium level the previous day and shows no clinical signs of hyperkalemia. The most likely pre-analytical explanation is:
Phlebotomy: Specimen Collection and Handling
6. Which information is required on a complete specimen label? Select the best answer.
Phlebotomy: Patient Preparation and Identification
7. During a role-play exercise, a student acting as the patient gives a date of birth that does not match the requisition. What should the phlebotomist student do next?
Phlebotomy: Specimen Collection and Handling
8. Which of the following actions is most likely to cause hemolysis in a venipuncture specimen?
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