Overview
Positive and negative (including no-template) controls are required molecular QC materials that confirm detection chemistry works and that unexpected target amplification is absent before patient results are released.
Classification
| Control | Protects against | Failure concern |
|---|---|---|
| Positive | Reagent/detection failure | False negatives / invalid not-detected calls |
| Negative / NTC | Contamination / nonspecific signal | False positives / invalid detected calls |
Morphologic Features
Not applicable, this entry covers molecular QC controls, not morphologic identification.
Laboratory Characteristics
- Pass/fail criteria are assay- and SOP-defined
- Instrument green status does not replace control review
- Document outcomes before LIS release
Reference Intervals
Not applicable as a numeric reference interval. Control acceptance is defined by the validated assay procedure and institutional SOP.
Clinical and Laboratory Significance
Control-first review gates both detected and not-detected reports. Failed positive or negative controls make routine patient release unsafe until SOP actions are complete.
Differential Considerations
Failed negative → consider contamination, reagent contamination, amplicon carryover. Failed positive → consider reagent degradation, setup error, instrument/detection failure. Do not invent a clinical story to override QC.
Comparison Tables
Positive/negative control checkpoints
| Statement | Safe understanding | Unsafe shortcut |
|---|---|---|
| Strong patient positives + failed NTC | Hold, contamination risk | Release 'obvious' positives |
| Quiet patients + failed positive | Hold, assay may have failed | Release as negatives |
| Daily controls vs EQA | Different questions; both useful | Treat them as interchangeable |
Classification Frameworks
Not applicable . WHO disease classifications do not define molecular positive/negative control QC.
Laboratory Notes
- Controls before patient targets
- Failed controls → hold and investigate
- Invalid ≠ negative; QC ≠ verification ≠ validation ≠ external assessment
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.
Frequently Asked Questions
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