Overview
Introduction to Liver Function Testing sits within the Module 5 liver function pathway. Core related markers include ALT, AST, ALP (± GGT), bilirubin (± fractions), albumin, and total protein.
Classification
| Element | Role | Bench link |
|---|---|---|
| ALT / AST | Hepatocellular injury enzymes | ALT more liver-selective; AST multi-tissue |
| ALP ± GGT | Cholestasis framing | GGT supports hepatic/biliary ALP origin |
| Bilirubin | Pigment / excretion marker | Fractionate; protect from light |
| Albumin / total protein | Synthetic / protein status | Not acute injury markers alone |
Morphologic Features
Chemistry marker reference, morphologic cell identification is hematology, not liver chemistry framing.
Laboratory Characteristics
- Confirm analyte units and bilirubin fraction naming
- Note ALP age/physiologic context when relevant
- Review HIL and other method flags before release
- Verify institutional reference intervals, not textbook dogma
Reference Intervals
Reference intervals and decision thresholds for liver markers are method-, age-, and population-dependent. Verify institutional and method-specific intervals, do not invent absolute universal cutoffs as dogma.
| Parameter | Reporting note | Action |
|---|---|---|
| ALT / AST | Method/age/sex intervals vary | Verify local RI |
| ALP / GGT | Age and physiologic states matter | Verify local RI + context |
| Bilirubin | Total ± direct/indirect naming varies | Confirm LIS fractions |
| Albumin / total protein | Method-specific intervals | Verify when offered |
Clinical and Laboratory Significance
An abnormal LFT panel may reflect hepatocellular injury, cholestasis, impaired synthesis, hemolysis/bilirubin overproduction, physiologic states, drugs, or analytical artifact, pattern recognition precedes disease labels.
Differential Considerations
Laboratory differentials for abnormal LFTs use hepatocellular, cholestatic, mixed, synthetic-impairment, and non-hepatic (muscle, bone, hemolysis) frames. Chemistry suggests patterns; clinical correlation completes assessment.
Comparison Tables
Hepatocellular vs cholestatic vs synthetic framing
| Frame | Typical lab clue | Caveat |
|---|---|---|
| Hepatocellular | ALT/AST-predominant elevation | Not etiology-specific |
| Cholestatic | ALP (± GGT) predominant; conjugated bilirubin may rise | Bone ALP confounder without GGT |
| Synthetic | Low albumin (± coagulopathy when ordered) | Many non-hepatic hypoalbuminemia causes |
Classification Frameworks
AASLD-oriented guidance and institutional protocols may frame evaluation of abnormal liver chemistries, always verify current institutional adoption; do not invent absolute universal cutoffs as dogma.
Laboratory Notes
- Never invent absolute universal diagnostic cutoffs as dogma
- Verify institutional and method-specific reference intervals
- Protect bilirubin specimens from light; confirm fraction naming
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
- 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).
- Clinical and Laboratory Standards Institute. Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Standard. CLSI document EP28-A3c. CLSI; 2010.
Frequently Asked Questions
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