8.2 Aliquoting

ASCP Medical Laboratory Assistant MLA

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1 Introduction & Exam Overview

1.1 About the ASCP MLA Exam 1.2 Eligibility Routes and Study Plan

2 Chapter 2: Orders, Identification & Communication

2.1 Review, Clarification, and Verification of Test Orders 2.2 Patient Identification 2.3 Patient Communication

3 Chapter 3: Collection Procedures

3.1 Patient Assessment and Preparation 3.2 Site Selection 3.3 Tubes, Anticoagulants, and Order of Draw 3.4 Specimen Types for Common Tests

4 Chapter 4: Special Collections, Reactions & Handling

4.1 Special Collection Procedures 4.2 Adverse Collection Reactions 4.3 Specimen Labeling and Immediate Handling

5 Chapter 5: Specimen Acceptability Assessment

5.1 Correct Specimen Type for the Test 5.2 Specimen Quality Assessment 5.3 Labeling Requirements and Rejection Criteria 5.4 Time, Temperature, and Light Handling

6 Chapter 6: Add-on Requests & Special Specimen Types

6.1 Specimen Suitability for Add-on Requests 6.2 Special Specimen Types

7 Chapter 7: Prioritization, Distribution & Transport

7.1 Department Distribution and Prioritization 7.2 Pneumatic Tube System 7.3 External Packaging and Shipment

8 Chapter 8: Specimen Processing Techniques

8.1 Centrifugation 8.2 Aliquoting 8.3 Non-Blood Specimen Processing 8.4 Microbiology Setup and Plating

9 Chapter 9: Slide Preparation & Specimen Storage

9.1 Slide Preparation 9.2 Specimen Storage (Pre- and Post-Testing)

10 Chapter 10: Reagents, Instrumentation & Quality Control

10.1 Reagents, Standards, and Controls 10.2 Analytical Instrumentation 10.3 Quality Control

11 Chapter 11: Critical Values, Results & Inventory

11.1 Critical Value Notification and Documentation 11.2 Result Retrieval and Review 11.3 Inventory Management

12 Chapter 12: Waived & Point-of-Care Testing

12.1 Waived and POC Instrument Operation 12.2 Waived/POC QC, Result Evaluation & Reporting

13 Chapter 13: Laboratory Regulations, Chemical & Fire Safety

13.1 Laboratory Regulations 13.2 Chemical Safety 13.3 Fire Safety

14 Chapter 14: Infection Control & Waste Disposal

14.1 Standard Precautions, PPE & Hand Hygiene 14.2 Biological Safety Cabinets, Sharps & Exposure Control 14.3 Biological and Hazardous Waste Disposal

15 Chapter 15: Equipment, Ethics, LIS & Quality Assurance

15.1 Laboratory Equipment Maintenance 15.2 Professionalism, Ethics & HIPAA 15.3 Laboratory Information System (LIS) Functions 15.4 Quality Assurance and Improvement

Key Takeaways Explain This Topic AI

Aliquot labels must carry the same critical identifiers as the parent specimen and remain linked to the accession in the LIS

Use clean technique—new pipette tips or pour paths per patient—to prevent cross-contamination; never return poured material to the primary tube

Separate serum/plasma from cells within validated times; prepare multiple labeled aliquots when send-outs require different temperatures or labs

Control aerosol risk with caps, careful pipetting, and PPE; prefer pour-off only when policy allows and identity control is maintained

Last updated: August 2026

8.2 Aliquoting

Quick Answer: An aliquot is a portion of a specimen moved into a secondary container. Label it with the same patient identifiers and accession linkage as the parent, transfer with clean technique (no shared tips or pour spouts across patients), separate serum/plasma on time, prepare multiple labeled aliquots for send-outs when needed, control aerosols , and never pour leftover aliquot back into the primary in a way that contaminates the original tube.

Aliquoting multiplies both efficiency and risk. One good SST can feed chemistry, a frozen send-out, and a reference lab—or one sloppy pour can contaminate three patients’ results. Domain II expects the MLA to aliquot accurately under time pressure without sacrificing identity or integrity.

Why Laboratories Aliquot

Reason Example
Instrument load Pour-off cups or sample cups for analyzers that do not pierce primary tubes
Send-out / reference testing Frozen aliquot shipped while primary stays on site
Multiple departments Chemistry + immunology sharing one draw
Stability Remove serum from cells; freeze labile analytes promptly
Archive / add-on protection Reserve volume under controlled storage
Special testing PPP aliquots for coag panels

Aliquoting is not a fix for wrong tube type, unlabeled specimens, or QNS magic. If the parent is unacceptable, the aliquot is unacceptable.

Labeling: Match the Parent

Every aliquot tube must be identifiable as if it were a primary.

Minimum expectations (policy detail varies):

Two patient identifiers (e.g., name + MRN/DOB) matching the parent and order
Accession or specimen ID linking to the LIS
Date/time of aliquot when required
Specimen type/matrix if not obvious (serum, EDTA plasma, urine, CSF)
Technologist/MLA initials when SOP requires
Storage condition mark (freeze, refrigerate, ambient) for send-outs

Workflow discipline:

Print or prepare aliquot labels from the correct accession —not freehand from memory.

Label the empty aliquot tube before or immediately as you transfer—never a rack of unlabeled “I’ll mark them later” cups.

Keep only one patient’s material open in the work zone when possible.

If a label will not scan or peels, stop and resolve identity before shipping or loading.

Mislabeling an aliquot is the same patient-safety event as mislabeling a draw. Do not “fix” a wrong secondary label by guessing which rack position was which.

Technique: Avoid Cross-Contamination
Pipette transfer (preferred for precision and many biosafety workflows)

Use a new disposable tip for each patient (and for each separate matrix if contamination between tubes matters).

Do not touch the tip to the outside of tubes or to non-sterile surfaces then re-enter the specimen.

Draw smoothly; avoid forceful expulsion that foams or aerosols.

For serum/plasma, pipette from the clear layer —do not disturb the gel, buffy coat, or cell button.

Change gloves if contaminated; decontaminate the work surface between messy jobs.

Pour-off technique

Some labs still pour from primary tubes into aliquot cups:

Cap or cover nearby open specimens.

Pour smoothly along the inner wall of the receiving tube; avoid spurting.

Do not touch the primary rim to the aliquot rim in a way that transfers residue from a previous pour.

Wipe exterior drips with disinfectant-appropriate technique; never lick labels or wipe with the same gauze across patients.

Prefer pour-off shields or cabinets when SOP requires for high-risk fluids.

Method Advantages Risks
Pipette Controlled volume; less rim contact Aerosols if blown out; tip carryover if reused
Pour-off Fast for bulk serum Splash, cross-rim contamination, identity errors if many tubes open
Never Pour Back Into the Primary

Returning aliquot material to the original tube can:

Introduce bacteria or environmental contaminants
Carry detergent or analyte residue from secondary tubes
Mix wrong-patient material if cups were confused
Dilute or concentrate the primary unpredictably

Rule: Once serum/plasma leaves the primary for an aliquot cup, treat that portion as committed. Excess in the secondary is discarded as biohazard waste per policy—or stored as a labeled residual aliquot—not dumped back into the SST “to keep it full.”

Also avoid pouring from patient A’s cup into patient B’s cup to “top off” volumes.

Serum/Plasma Separation Timing

Cells continue to metabolize and leak analytes if left in contact with serum/plasma.

Concern Why timing matters
Glucose Cellular glycolysis lowers glucose unless fluoride or prompt separation
Potassium Leakage from cells raises K+ over time, especially with cold or delay
LDH, AST, phosphate Cell leakage patterns
Coagulation factors Time and temperature limits from draw to test/freeze

General MLA practice:

Centrifuge within the maximum time from collection stated for that tube/test.

Aliquot or load analyzers promptly after spin for labile work.

Do not leave spun tubes uncapped for long periods (evaporation, contamination, CO₂ loss affecting some assays).

For send-outs, freeze or refrigerate aliquots as the send-out manual specifies —not all analytes share the same condition.

Multiple Aliquots for Send-Outs

Reference work often needs more than one tube:

Send-out need Aliquot strategy
Different temperatures Separate frozen vs refrigerated aliquots, each labeled
Different reference labs Separate labeled tubes per destination
Repeat testing / QNS protection Split volume only if each aliquot still meets minimums
Light-sensitive tests Amber tubes or foil; minimize light during pour
Infectious workups Follow packaging rules; never overfill; seal threads

Check minimum volumes for each send-out before splitting so you do not create three QNS tubes from one adequate primary. If volume is limited, prioritize per laboratory and clinical urgency—escalate rather than guessing.

Document which aliquot went where when the LIS supports aliquot IDs.

Aerosol Risk

Opening tubes, popping stoppers, forceful pipetting, and centrifuge failures generate aerosols —fine droplets that can carry pathogens.

Controls:

PPE: gloves always; face protection when splash risk is significant; lab coat/gown
Open tubes with gauze or stopper-removal devices pointing away from the face
Avoid “popping” vacuum tubes toward yourself
Use aerosol-resistant tips when SOP specifies
Work in a biosafety cabinet for designated high-risk specimens if required by policy
Cap aliquots immediately after transfer
Clean spills at once with approved disinfectant and contact time

Body fluids, respiratory specimens, and known high-risk samples deserve extra caution even when “only aliquoting.”

Quality Checks on Aliquots

Before releasing aliquots to instruments or couriers:

Identity: label vs parent vs LIS
Volume adequacy
Visual quality: hemolysis, lipemia, icterus, clots/fibrin
Correct matrix noted
Cap sealed; no exterior gross contamination
Correct storage rack/temperature

If the primary was hemolyzed, the aliquot is hemolyzed— do not assume filtration or “clear top layer” fixes free hemoglobin for potassium.

Workflow Snapshot

Verify parent acceptability and orders.

Generate labels for the correct number of aliquots.

Spin if needed; inspect barrier and serum/plasma.

Transfer with single-patient focus and clean tips/pour technique.

Cap, store, or route; document send-outs.

Discard waste and decontaminate the bench.

Never return poured material to the primary; never share pipette tips across patients.

Key Takeaways

Aliquot labels = parent identity + accession linkage —no unlabeled cups.

Prevent cross-contamination with one tip/one patient and careful pour-offs.

Separate and aliquot within stability windows ; split send-outs into correctly stored, labeled tubes.

Respect aerosol precautions when opening and pipetting.

Never pour back into the primary in ways that contaminate or confuse identity.