Overview
Sodium concentration in serum/plasma measured by ion-selective electrode (direct or indirect).
Clinical Importance
Detect hypo-/hypernatremia
Electrolyte panel staple
Specimen Requirements
- Specimen: serum or lithium heparin plasma (method- and analyzer-dependent; follow the performing laboratory)
- Tube: gold/SST (serum separator) or green-top lithium heparin as validated locally
- Handling: invert gently; allow SST to clot fully before centrifugation; separate promptly
- Storage: refrigerate serum/plasma if testing is delayed per analyte stability limits
- Stability: analyte-specific; do not exceed institutional or manufacturer time/temperature limits
Analytical Method
Potentiometric ISE. Indirect ISE (diluted) can show pseudohyponatremia with extreme hyperlipidemia/hyperproteinemia; direct ISE (undiluted/blood gas) is less affected.
Instruments Used
Automated analyzers
- Roche Cobas chemistry and immunoassay systems
- Abbott Alinity / Architect chemistry and immunoassay systems
- Siemens Healthineers Atellica / ADVIA chemistry and immunoassay systems
- Beckman Coulter AU / DxC chemistry systems
- Beckman Coulter Access / DxI immunoassay systems
- Mindray BS-series chemistry analyzers
- Ortho Clinical Diagnostics Vitros systems
- Thermo Fisher / Indiko and related chemistry platforms
- Randox clinical chemistry systems
Manual methods
- Manual spectrophotometric/immunoassay methods in selected reference or backup settings
Reference Values
Typical adult SI examples below follow widely published international clinical chemistry practice (e.g., Tietz; Henry's). Always interpret against the method- and demographics-specific interval printed on the patient report (CLSI EP28-A3c). Neonatal, pediatric, pregnancy, and assay-generation intervals differ.
Typical published adult serum sodium often 135–145 mmol/L.
Interpretation
Critical and significant-risk limits are institution-defined (CLSI GP47). Confirm the local call list. Textbook examples are not universal thresholds.
Critical values
- Severe hypo-/hypernatremia commonly critical; verify local thresholds
Common Causes of Increased Results
- Hypernatremia; free water deficit patterns
Common Causes of Decreased Results
- Hyponatremia; interpret with osmolality and clinical volume status
Clinical Significance
- Electrolyte and fluid-balance assessment
Factors Affecting Results
Pre-analytical
- Hemolysis, lipemia, or icterus (analyte- and method-dependent interference)
- IV fluid contamination or draw above an infusion
- Prolonged tourniquet time; delayed separation of cells
- Wrong tube additive or incomplete clotting of SST
- IV fluid contamination (hypotonic or hypertonic)
Analytical
- Indirect ISE pseudohyponatremia with marked lipemia/paraprotein
Post-analytical
- Wrong reference interval or unit applied
- Failure to review delta checks / critical values before release
Advantages and Limitations
Advantages
- Rapid ISE measurement
Limitations
- Indirect ISE artifact in extreme protein/lipid states
Clinical Pearls
Odd hyponatremia with creamy serum? Repeat on direct ISE or check lipids/protein before treating the number.
References
Authoritative textbooks, guidelines, and reviews supporting this laboratory test reference. Verify reference intervals, critical limits, and method details 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
- International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). Recommendations and reference measurement systems for clinical chemistry measurands (verify current IFCC documents for the analyte).
- 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.
- American Diabetes Association. Standards of Care in Diabetes. Diabetes Care (annual update).
- Kidney Disease: Improving Global Outcomes (KDIGO). Clinical Practice Guideline for Evaluation and Management of Chronic Kidney Disease.
- American Association for the Study of Liver Diseases (AASLD). Practice guidance related to evaluation of abnormal liver chemistries / liver disease laboratory evaluation (verify current AASLD publication and institutional adoption).
Frequently Asked Questions
Common questions about using this Sodium laboratory test Medical Laboratory Library reference in Medical Laboratory Science education.
What is the Sodium laboratory test reference used for?
This Medical Laboratory Library page summarizes the clinical importance of Sodium. Review the Clinical Importance section for why the test is ordered in laboratory medicine practice.
Where can I find Sodium specimen requirements?
See the Specimen Requirements section on this page for specimen information related to Sodium. Confirm collection details against your laboratory protocol.
Where are Sodium reference values listed?
See the Reference Values section on this Laboratory Library page. Reference ranges can vary by method and population, so verify intervals with your laboratory.
How do I interpret Sodium results?
Use the Interpretation section for laboratory interpretation framing, including increased and decreased result patterns when provided. Do not treat educational text as a patient-specific diagnosis.
What analytical method is used for Sodium?
See the Analytical Method section for principle and method notes. Method details may differ by instrument and institutional SOP.
Are related laboratory tests linked from Sodium?
Yes. The Related Laboratory Tests section lists connected references for continued lookup in the Medical Laboratory Library.
How can I continue learning after reading Sodium?
Use Continue learning links on this page for related Academy lessons, medical laboratory quizzes, or laboratory case studies when available for this Clinical Chemistry topic.
What are the clinical pearls for Sodium?
See the Clinical Pearls section for concise laboratory practice notes associated with Sodium. Apply pearls alongside institutional protocols.
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