Does a Comprehensive Metabolic Panel Include AST and ALT?
No, a standard Comprehensive Metabolic Panel (CMP) does not include AST or ALT measurements. These liver enzymes must be ordered separately as part of a hepatic function panel or liver function tests (LFTs).
What a CMP Actually Measures
A standard CMP is a 14-component blood test that includes:
- Metabolic markers: Glucose, calcium
- Electrolytes: Sodium, potassium, chloride, bicarbonate
- Kidney function: Blood urea nitrogen (BUN), creatinine
- Liver-related proteins: Total protein, albumin, total bilirubin
- Alkaline phosphatase (ALP): The only enzyme routinely included that relates to liver/biliary function
Why AST and ALT Are Not in a CMP
While the CMP includes some liver-related markers (albumin, bilirubin, ALP), it does not contain the aminotransferases (AST and ALT) that are essential for detecting hepatocellular injury 1.
To monitor AST and ALT, you must specifically order:
- A hepatic function panel (HFP)
- Liver function tests (LFTs)
- Individual AST and ALT tests
Clinical Importance of AST and ALT Monitoring
AST and ALT are critical markers that should be routinely measured when liver disease is suspected or being monitored 1:
- ALT is more liver-specific and is considered the most reliable biomarker for hepatocellular disease 1, 2, 3
- AST is less specific as it is present in cardiac muscle, skeletal muscle, kidneys, brain, and red blood cells 2
- AST/ALT ratio >2:1 is highly suggestive of alcoholic liver disease, while ratios <1 suggest NAFLD 1, 2
- AST elevation alone can occur from muscle injury, rhabdomyolysis, myocardial infarction, or hemolysis 2
When to Order AST and ALT
These enzymes should be specifically requested in the following scenarios 1:
- Screening for chronic liver disease in at-risk populations (diabetes, obesity, alcohol use)
- Monitoring patients on potentially hepatotoxic medications
- Evaluating abnormal CMP results (elevated bilirubin or ALP)
- Assessing fibrosis risk using calculated scores (FIB-4, NFS, APRI) which require AST and ALT values 1
- Following patients with known liver disease
Common Clinical Pitfall
Do not assume liver function is adequately assessed by a CMP alone. A normal CMP with normal bilirubin, albumin, and ALP can still miss significant hepatocellular injury that would be detected by elevated ALT 1, 3. In primary care screening for liver disease, a restricted panel of ALT and ALP is the most efficient combination for detecting both hepatocellular and biliary disease 3.