Overview
Chemistry tube selection is based on the additive printed on the tube, desired matrix, separator, and assay-specific restrictions, not cap color alone. 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 |
|---|---|---|
| Plain/clot activator | Serum | Allow complete clotting |
| SST | Serum with gel | Inspect barrier |
| Lithium heparin/PST | Plasma with or without gel | Check analyte restriction |
| EDTA/fluoride products | Specialized uses | Not routine substitutes |
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
Additive contamination can produce a convincing but false chemistry pattern, such as potassium elevation with calcium depression after EDTA contamination. 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
Safe chemistry tube selection
| Feature | Tube selected by additive | Tube selected by color |
|---|---|---|
| Evidence | Printed tube label | Visual convention |
| Reliability | Manufacturer-specific | May vary |
| Safety | Method matched | Contamination risk |
Classification Frameworks
WHO disease classifications are not the primary framework for preanalytical chemistry specimen terminology.
Laboratory Notes
- Tube color conventions can differ by manufacturer and region
- Maintain a current collection manual linked to each test code
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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