Overview
A reference interval is the range of values expected for a defined reference population measured by a specific method under stated conditions. Critical values are separately defined notification limits.
Classification
| Concept | Defines | Action |
|---|---|---|
| Reference interval | Statistical expectation | H/L flagging |
| Decision limit | Clinical action threshold | Protocol-driven care |
| Critical value | Urgent notify threshold | Immediate call per policy |
Morphologic Features
Intervals reference, not morphologic.
Laboratory Characteristics
- Partition by age/sex when required
- Verify intervals after major method changes
- Display units clearly on all reports
Reference Intervals
Numeric examples are intentionally omitted here, verify institutional intervals and critical lists locally.
| Unit topic | Example pair (concept) | Note |
|---|---|---|
| Glucose | mg/dL ↔ mmol/L | Conversion factor required |
| Creatinine | mg/dL ↔ µmol/L | Method-dependent baselines |
| Bilirubin | mg/dL ↔ µmol/L | Keep unit system consistent |
Clinical and Laboratory Significance
Correct intervals and units prevent false clinical alarms and missed critical states.
Differential Considerations
Differentiate true physiologic change from unit error, wrong partition, or method shift when results look discrepant.
Comparison Tables
RI vs critical
| Feature | Reference interval | Critical value |
|---|---|---|
| Basis | Reference population statistics | Clinical urgency policy |
| Flag type | H/L atypical vs reference | Critical alert |
| Response | Interpret in context | Immediate notification |
Classification Frameworks
Not applicable.
Laboratory Notes
- Never invent critical limits from memory on the phone
- Cite method notes when clinicians compare across platforms
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.
Frequently Asked Questions
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Can reference details vary between laboratories?
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