LabQMHub Editorial Team · ISO 15189:2022 Quality Management Series
It is one of the most counterintuitive facts in laboratory medicine: the majority of testing errors occur before a specimen ever reaches an analyzer. Test ordering mistakes, patient misidentification, improper collection technique, and transport delays account for a disproportionate share of laboratory-related diagnostic error — far more than analytical failures at the bench.
ISO 15189:2022 addresses this reality directly through Clause 7.2, Pre-examination processes, which governs everything from how a test is ordered to how a specimen arrives ready for analysis. Understanding this phase is essential for any laboratory serious about reducing its overall error rate.
Why the Pre-Examination Phase Carries So Much Risk
Unlike the analytical phase, which occurs entirely within the laboratory’s controlled environment, pre-examination activities often happen outside direct laboratory oversight — at a nursing station, in a phlebotomy room, during transport by courier — where laboratory staff have less direct control over technique and conditions. This distributed responsibility is precisely why errors here are both more common and harder to systematically prevent.
A wrong test order, a mislabeled tube, or a specimen collected in the wrong additive can produce a result that looks perfectly plausible to the analyzer while being clinically meaningless or dangerously misleading — making pre-examination errors especially insidious, since they often escape detection until a clinician questions an unexpected result.
Patient and Specimen Identification: The First Line of Defense
Positive patient identification at the point of collection, using at least two independent identifiers, is one of the most consequential controls in the entire pre-examination process — a single identification failure can lead to a specimen being attributed to the wrong patient entirely, with results that then guide treatment for someone else’s condition. ISO 15189:2022 requires laboratories to have clear, enforced procedures for this step, with no exceptions made for familiarity or urgency.
Specimen labeling at the bedside or collection point, before the collector leaves the patient, closes the gap where mislabeling most commonly occurs — labeling specimens later, away from the patient, reintroduces exactly the risk positive identification was meant to eliminate.
Collection, Handling, and Transport Requirements
Specimen collection technique — correct tube type, appropriate order of draw, adequate volume, and proper mixing — directly affects whether a specimen remains valid for testing, and ISO 15189:2022 expects laboratories to provide clear collection instructions and training to everyone involved in the process, including staff outside the laboratory’s direct management.
Transport conditions matter just as much as collection technique: temperature control, time-to-testing limits, and protection from light or agitation for sensitive analytes must be maintained throughout transport, connecting directly to the environmental monitoring principles covered earlier in this program’s facilities course.
Specimen Rejection Criteria and Acceptable Exceptions
Laboratories must define objective criteria for rejecting unsuitable specimens — hemolysis, clotting, insufficient volume, incorrect container, or excessive transport delay — and apply these criteria consistently rather than making exceptions under clinical pressure that compromise the reliability of the eventual result.
At the same time, ISO 15189:2022 recognizes that some irreplaceable specimens may require documented exception handling, with the resulting report clearly flagging any limitation this exception may have introduced, so the receiving clinician can interpret the result with appropriate caution rather than false confidence.
Frequently Asked Questions
Why is patient identification considered so critical in the pre-examination phase?
A misidentified specimen can lead to a completely wrong patient’s results guiding treatment decisions, making identification errors among the most dangerous and consequential mistakes in the entire testing process.
What are common reasons a laboratory rejects a specimen?
Hemolysis, clotting in an anticoagulated tube, insufficient volume, incorrect collection container, mislabeling, and excessive delay between collection and receipt are among the most common rejection criteria.
Can a laboratory ever accept a specimen that doesn’t meet normal criteria?
In limited, documented circumstances involving irreplaceable specimens, yes — but the resulting report should clearly flag the limitation so the result is interpreted with appropriate clinical caution.
Key Takeaways
- The pre-examination phase, not the analytical phase, is the leading source of laboratory-related diagnostic error.
- Positive patient identification using at least two independent identifiers is one of the most consequential controls in the entire testing process.
- Specimen labeling at the point of collection, before leaving the patient, prevents the most common source of mislabeling error.
- Collection technique and transport conditions must be controlled and monitored, even when performed by staff outside the laboratory’s direct management.
- Objective, consistently applied specimen rejection criteria protect result reliability, even under clinical pressure to make exceptions.
- Any accepted exception to rejection criteria should be clearly flagged on the report so clinicians interpret the result appropriately.
Conclusion
Opening Track 4 of this training program with pre-examination processes is deliberate: no amount of analytical excellence can compensate for a poorly collected, mislabeled, or improperly transported specimen. This is where laboratory quality genuinely begins.
ISO 15189:2022’s pre-examination requirements exist to extend the laboratory’s quality discipline outward, into the collection points and transport chains it does not always directly control, but remains fully accountable for.
Continue through the total testing process with the next course in this series, covering examination method verification and validation.
Source note: this article draws on “Quality Management in Clinical Laboratory Demystified” by Dr. Taleb Chalab Cham, ISO 15189:2022, and widely recognized clinical laboratory quality references including CLSI guidelines, CAP accreditation checklists, and WHO laboratory quality guidance.
