Overview
Plasma is the cell-free liquid from anticoagulated blood; its additive, fill volume, mixing, and assay validation determine whether it is suitable. Valid chemistry results require the correct patient, specimen, matrix, container, processing conditions, and documented chain from collection through analysis.
Classification
| Category | Key characteristic | Bench implication |
|---|---|---|
| Lithium heparin | Common chemistry plasma | Avoid for lithium measurement |
| Sodium heparin | Method-dependent use | Adds sodium |
| EDTA plasma | Chelates divalent ions | Unsuitable for many chemistry assays |
| Citrate plasma | Liquid additive and dilution | Primarily coagulation; method-specific |
Morphologic Features
Preanalytical reference, morphologic cell identification is hematology, not clinical chemistry specimen handling.
Laboratory Characteristics
- Inspect identity, container, volume, and visible integrity before analysis
- Verify clotting, mixing, centrifugation, time, and temperature requirements
- Apply H-index/L-index/I-index and rejection rules by assay and SOP
Reference Intervals
Numeric HIL cutoffs, clotting times, centrifuge settings, and stability windows are method- and institution-specific. Verify against local SOP and package inserts, do not treat textbook examples as universal critical limits.
| Concept | Meaning | Notes |
|---|---|---|
| Institutional threshold | SOP/method-defined acceptability limit | Verify locally |
| H / L / I index | Hemolysis / lipemia / icterus interference flags | Assay-specific |
| Stability window | Time/temperature for valid analysis | Analyte- and matrix-specific |
Clinical and Laboratory Significance
Plasma may shorten turnaround by avoiding clot time, but an inappropriate additive can invalidate electrolyte, trace element, or enzymatic results. A preanalytical failure can create a misleading chemistry pattern and must be resolved before diagnostic interpretation.
Differential Considerations
Differentiate true patient change from wrong matrix, additive carryover, cellular leakage, contamination, delayed separation, or optical interference.
Comparison Tables
Plasma acceptability at the chemistry bench
| Feature | Well-prepared plasma | Compromised plasma |
|---|---|---|
| Additive | Correct | Wrong or uncertain |
| Clots | Absent | Present/microclots |
| Action | Analyze | Reject or recollect per SOP |
Classification Frameworks
WHO disease classifications are not the primary framework for preanalytical chemistry specimen terminology.
Laboratory Notes
- Underfill consequences vary by tube and method; verify institutional criteria
- Never use lithium-heparin plasma for a lithium assay
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. Collection of Diagnostic Venous Blood Specimens. CLSI standard GP41. CLSI.
- Clinical and Laboratory Standards Institute. Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Standard. CLSI document EP28-A3c. CLSI; 2010.
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