Liver Function Tests (LFTs)
Start with the big picture
The core LFT panel includes total and direct bilirubin, ALT, AST, ALP, GGT, albumin, total protein, and PT/INR. ALT is more specific to liver injury, whereas AST can also arise from muscle and other tissues. The R-ratio uses ALT and ALP relative to their upper limits of normal to classify results as hepatocellular, cholestatic, or mixed. ALP may have non-hepatic sources, so GGT or 5′-nucleotidase can help confirm a hepatic origin. Bilirubin, albumin, and PT/INR provide additional context about excretion and synthetic function. Results require clinical interpretation: isolated abnormalities and patterns can have multiple explanations, and adjunctive markers may be used when specific disorders are considered.
What you'll learn
- Identify the core components of an LFT panel and their broad clinical roles.
- Distinguish hepatocellular, cholestatic, and mixed patterns using the R-ratio.
- Explain how GGT or 5′-nucleotidase can clarify an elevated ALP.
- Describe how bilirubin, albumin, and PT/INR contribute to interpretation.
- Recognize the roles and limitations of selected adjunctive markers.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
