Overview
Selecting the correct specimen in molecular diagnostics means confirming that the received sample type, device, and matrix match what the ordered, validated assay accepts. Requirements are defined by the assay and laboratory procedure, not by a single universal specimen rule.
Classification
| Decision | Acceptable approach | Unsafe approach |
|---|---|---|
| Specimen type | Use type listed for that assay | Substitute a 'similar' matrix |
| Uncertainty | Hold and verify SOP/IFU | Process to avoid recollection |
| Mismatch at receipt | Reject/recollect per SOP | Extract anyway and 'note it' |
Morphologic Features
Not applicable, this entry covers specimen-to-assay matching, not morphologic identification.
Laboratory Characteristics
- Assay menus differ across platforms and institutions
- Device and transport medium often matter as much as body site
- Preanalytical mismatch can invalidate an otherwise well-run amplification
Reference Intervals
Not applicable, specimen selection is a qualitative acceptability decision, not a numeric reference interval.
Clinical and Laboratory Significance
Correct specimen selection is required for trustworthy molecular results. Poor or mismatched specimens can produce false-negative, invalid, or unreliable findings that mislead clinical decisions.
Differential Considerations
Before attributing a 'not detected' result to true target absence, confirm the specimen type was validated for the assay, an unvalidated matrix can mimic a true negative.
Comparison Tables
Specimen selection checkpoints
| Question at receipt | Safe action | Unsafe action |
|---|---|---|
| Does this tube/site match the ordered assay? | Yes → proceed per SOP | Assume yes because IDs match |
| Is serum allowed when plasma is listed? | Only if SOP/IFU says yes | Treat as interchangeable |
| Can we 'make do' to save a draw? | No, follow rejection pathway | Run and add a comment |
Classification Frameworks
Not applicable . World Health Organization (WHO) disease classifications do not define molecular specimen acceptance rules.
Laboratory Notes
- Collection devices, transport media, storage, and acceptance criteria depend on the validated assay and manufacturer/laboratory procedure
- Wrong specimen type is a preanalytical failure, stop and resolve before extraction
- Poor specimens → false-negative, invalid, or unreliable results
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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