Overview
Contamination patterns are control and batch signatures suggesting unintended target entered clean reactions or reagents. Interpretation means recognizing the pattern, holding release, and investigating per SOP before any disease language.
Classification
| Pattern | Safe response |
|---|---|
| Negative control amplifies | Hold; investigate per SOP |
| Unexpected positive cluster | Do not release as independent infections |
| Post-PCR near clean setup | Stop breach pathway; follow contamination response |
| Valid retest after cleanup | Interpret clean results with validated wording only |
Morphologic Features
Not applicable, contamination patterns are process and run-validity findings, not morphologic diagnoses.
Laboratory Characteristics
- Amplicon, specimen, and reagent pathways can all create false positives
- Unidirectional workflow protects clean areas from amplicon carryover
- Ct/Cq strength does not prove a positive is non-contaminated
Reference Intervals
Not applicable as a numeric reference interval. Run acceptance depends on control rules and institutional contamination-response procedures.
Clinical and Laboratory Significance
Releasing contaminated positives drives false clinical action. Renaming a compromised batch as all-negative is also unsafe. Keep positive ≠ disease and invalid ≠ negative as paired safety lines.
Differential Considerations
Distinguish true patient positives on a valid run from contamination-driven detections, identity mix-ups, and nonspecific assay artifacts. Sort with controls and process review, not clinical hope.
Comparison Tables
Contamination interpretation checkpoints
| Finding | Safe understanding | Unsafe shortcut |
|---|---|---|
| Failed negative control | Compromised run, hold | Release likely-looking patient positives anyway |
| Strong low Ct positive | Method-dependent readout; still check controls | Proves contamination impossible |
| Contaminated batch | Investigate/repeat per SOP | Report everyone negative to clear phones |
Classification Frameworks
Not applicable . WHO classifications do not replace molecular contamination-control and run-validity rules.
Laboratory Notes
- Controls and batch pattern before patient disease language
- Positive ≠ always active disease; invalid ≠ negative
- Avoid unsupported diagnostic certainty in urgent notifications
References
Authoritative textbooks, guidelines, and reviews supporting this reference entry. Verify reference intervals, critical limits, and reflex criteria against institutional protocols and current guideline editions.
Textbooks
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021. (Molecular diagnostics chapters, verify current edition.)
- Buckingham L. Molecular Diagnostics: Fundamentals, Methods, and Clinical Applications. 3rd ed. F.A. Davis; 2019. (Verify current edition.)
CLSI and Professional Guidelines
- Clinical and Laboratory Standards Institute (CLSI). Consult current CLSI molecular method documents available through your laboratory, document numbers and editions change; do not treat any single CLSI title as universal.
- Institutional molecular laboratory SOPs, assay manufacturer instructions for use (IFU), and locally adopted accreditation requirements. Always verify current local practice.
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