Overview
Chemistry specimen types are defined matrices and additives from which chemical analytes are measured. Acceptability is assay- and platform-specific.
Classification
| Matrix | Additive concept | Routine chemistry role |
|---|---|---|
| Serum | Clot activator ± gel | Many panels |
| Plasma | Heparin (commonly Li) | STAT chemistry |
| Whole blood | Heparinized / POC | Selected rapid tests |
| Urine | None or preservative | Urine chemistries |
Morphologic Features
Specimen matrix reference, not morphologic cell ID.
Laboratory Characteristics
- Verify tube type at receipt
- Observe fill volumes and mixing requirements
- Separate cells within stability limits
Reference Intervals
Some analytes have matrix-specific reference intervals (serum vs plasma). Verify method claims.
Clinical and Laboratory Significance
Correct matrix selection prevents false critical electrolytes and invalid monitoring trends.
Differential Considerations
Extreme K or Ca, consider wrong tube/contamination before disease attribution.
Comparison Tables
Serum vs heparin plasma
| Feature | Serum | Heparin plasma |
|---|---|---|
| Clotting | Required before spin | Prevented by heparin |
| Turnaround | Longer (clot time) | Often faster for STAT |
| K nuance | May be slightly higher vs plasma | Method-dependent |
Classification Frameworks
Not applicable.
Laboratory Notes
- Follow CLSI GP41 principles for venous collection quality
- Never relabel another patient’s tube to “save” a draw
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
- Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 8th ed. Elsevier; 2022.
- McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021.
- Bishop ML, Fody EP, Schoeff LE. Clinical Chemistry: Principles, Techniques, and Correlations. 9th ed. Jones & Bartlett; 2022.
CLSI and Professional Guidelines
- Clinical and Laboratory Standards Institute. Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Standard. CLSI document EP28-A3c. CLSI; 2010.
- Clinical and Laboratory Standards Institute. Collection of Diagnostic Venous Blood Specimens. CLSI standard GP41. CLSI.
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