Unit 2: Sample and results management
Medical Laboratory Management notes · PTU syllabus (BMLS503-18)
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Unit summary
Most laboratory errors happen before or after the test itself. This unit covers patient management for sample collection, transport and preservation, sample accountability, factors affecting analysis, and reporting — formats, reference ranges, critical alerts, abnormal results, turnaround time, referral results and report alteration.
After this unit you can
- Prepare patients and collect, transport and preserve samples
- Ensure sample accountability and identify factors affecting analysis
- Prepare reports with reference ranges and critical alerts
- Manage turnaround time, referrals and amended reports
PTU syllabus topics
- Patient management for sample collection
- transportation and preservation
- sample accountability
- factors affecting sample analysis
- reporting results — test report format
- reference ranges
- clinical alerts
- abnormal results
- turnaround time
- referral lab results
- report alteration
- 1
Test request
- 2
Patient preparation and sample collection
- 3
Transport and accessioning
- 4
Analysis
With quality control
- 5
Verification and reporting
Flag critical values
- 6
Interpretation by the clinician
Topic 1
Patient management and sample collection
- Fasting
- 8–12 hours for glucose and lipids
- Timing
- Cortisol in the morning; drug levels at trough or peak
- Posture and rest
- Seated 15 minutes for some tests
- Medications
- Note anticoagulants, supplements (biotin affects immunoassays)
- Identification
- At least two identifiers (name and ID or date of birth)
- Consent and explanation
- Especially for HIV and invasive tests
- 1 Blood culture bottles
- Broth
- 2 Light blue
- Sodium citrate
- 3 Red or gold
- Clot activator or gel
- 4 Green
- Heparin
- 5 Lavender
- EDTA
- 6 Grey
- Fluoride–oxalate
Topic 2
Transport and preservation
- Transport upright, capped, in leak-proof bags and boxes with absorbent material (triple packaging for referrals); maintain temperature (ice for ammonia and blood gases; room temperature for coagulation; protect bilirubin from light); deliver within set times; separate serum within 2 hours.
Topic 3
Sample accountability
- Chain of custody from collection to disposal: unique barcode, request form matched to label, receipt log with time, rejection log. Rejection criteria: unlabelled or mislabelled, haemolysed, clotted (for CBC or coagulation), insufficient volume, wrong tube, leaking, delayed.
Topic 4
Factors affecting sample analysis
Biological
Age, sex, pregnancy, diet, exercise, circadian rhythm
Different reference intervals
Collection
Prolonged tourniquet, drawing above an IV line, wrong tube
Raised proteins and calcium; dilution; EDTA contamination
Sample quality
Haemolysis, lipaemia, icterus
Raised K⁺, LDH, AST; optical interference
Storage and transport
Delay, temperature
Low glucose, high K⁺, unstable factors
Drugs and substances
Biotin, vitamin C, heterophile antibodies
Immunoassay and chemistry interference
Topic 5
Reporting results
- Header
- Laboratory name, address, accreditation
- Patient details
- Name, age, sex, ID, referring doctor
- Sample details
- Type, collection and receipt times
- Results
- Test, value, units, method, reference interval, flags (H or L)
- Comments
- Interpretation, limitations
- Authorisation
- Signature of the authorised signatory, date and time of report
- Reference ranges: usually central 95% of a healthy population; adjusted for age and sex; method-specific.
- Critical (panic) values: life-threatening results (potassium above 6.5 mmol/L, glucose below 40 mg/dL, platelets below 20,000/µL, positive blood culture) telephoned to the clinician immediately and the call documented.
- Abnormal results: verify (repeat, check sample, delta check) before release.
Topic 6
Turnaround time, referral results and report alteration
- Turnaround time (TAT): time from sample receipt (or request) to report — set targets (e.g., emergency tests within 1 hour) and monitor as a quality indicator.
- Referral laboratories: results from referral labs are reported with the referral lab's name and accreditation, and copies kept.
- Report alteration: once released, a report may be amended only with documentation — original result retained, reason recorded, revised report clearly labelled "amended", clinician informed.
Key terms
- Order of draw
- Sequence for filling tubes to avoid additive carry-over
- Chain of custody
- Documented sample handling from collection to disposal
- Pre-analytical error
- Error before testing, such as wrong tube or haemolysis
- Critical value
- Result requiring immediate clinical notification
- Turnaround time
- Time from receipt to report
Quick revision
- Patient preparation; two identifiers; order of draw.
- Transport conditions; triple packaging.
- Accountability; rejection criteria.
- Biological, collection, quality, storage and drug factors.
- Report format; reference ranges; critical values; TAT; referral reports; amended reports.
Important exam questions
Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).
Short-answer questions
- Q1.Why is fasting required for lipid tests?
- Q2.Why are EDTA tubes drawn after citrate and serum tubes?
- Q3.Give three sample rejection criteria.
- Q4.How does haemolysis affect potassium?
- Q5.What is a critical value?
- Q6.How should a released report be corrected?
Long-answer questions
- Q1.Describe patient preparation, sample collection and transport.
- Q2.Describe pre-analytical factors affecting laboratory results.
- Q3.Describe the components of a laboratory report, critical values and turnaround time.
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