Making Sense of LFTs

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Making Sense of LFTs

• Alliance of Internal Medicine
• October 2004

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acknowledgments

• Images used in this presentation were downloaded
  from Google Images and are being used for the
  express purpose of education

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Markers for the Liver

• Detect the presence of liver disease
• Distinguish among different types of liver
  disorders
• Gauge the extent of known liver damage
• Follow the response to treatment

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LFTs is Not the Correct Term

• Liver Function Tests suggests that what we are
  measuring is the function of the liver
• Standard lab tests actually measure injury to
  hepatocytes, or altered bile flow
• Also be careful about speaking about a liver
  panel

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Risk Factors for Liver Disease

• Age and gender lifestyle / genetic
  predisposition
• Hemochroamtosis , alpha1- antitrypsin deficiency,
  Wilsons disease (generally rare)
• Exposure risk family with hepatitis
• Alcoholism, diabetes, hyperlipidemia

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Personal Habits and Exposures

• Alcohol use
• Exposure to blood/ blood products
• Sexual history
• Prior biliary surgery

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Physical ExaminationJaundice
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Spider Angioma
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Asterixis
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Caput medusa
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Nodular Liver
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Ascites
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Gynecomastia
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Muscle Wasting
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Laboratory Findings
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Hepatocellular Injury

• Aspartate aminotransferase (AST)
• Alanine aminotransferase (ALT)

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Aminotransferases

• Aspartate Aminotransferase (AST)
• In the mitochondria and cytosol
• Cardiac, kidney, skeletal muscle, brain

• Alanine aminotransferase (ALT)
• In the cytosol
• Primarily in the liver

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• High concentration in the hepatocytes
• Liver cell injury releases
• Elevation guides you to the liver but not to
  the cause

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Generalizations

• AST ALT
• Equal elevation viral / toxic injury
• Extremely high ischemia
• AST ALT 21 or greater alcohol
• REMEMBER THAT AST is not only from liver

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Ductular Injury and Cholestasis

• Alkaline phosphatase
• Bilirubin

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Alkaline Phosphatase

• Canalicular region of the hepatocytes
• Bile duct cells
• Ductular obstruction and cholestatsis leads to
  increased production of Alk phos and the release
  of alk phos from damaged cells

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Alkaline Phosphatase

• Elevations
• 4x normal highly suggestive of ductular injury
• Intrahepatic cholestasis
• infiltrative processes
• extrahepatic biliary obstruction
• primary sclerosing cholangitis
• malignant liver disease
• Lesser increase viral hepatitis, cirrhosis,
  congestive hepatopathy

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Alkaline Phosphatase

• Where else does it come from
• bone, adrenal cortex, placenta, intestine,
  kidney, lungs, leukocytes
• (bone and liver are primary source)
• Differentiation
• Fractionation
• 5-nucleotidase measure
• gamma-glutamyl transpeptidase (GGT)

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Bilirubin

• Breakdown of red blood cells
• Bilirubin cycle
• Hepatic uptake from the circulation
• Intracellular conjugation of bilirubin
• Canalicular secretion of bilirubin
• Conjugated bilirubin direct
• Unconjugated indirect

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Bilirubin

• Why increased?
• liver / ductal disease
• Red cell breakdown
• Is the urine dark?
• Conjugated bilirubin

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Liver Synthetic Function

• Albumin
• Clotting cascade

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Albumin

• Useful test of hepatic synthetic function
• Better for chronic than acute because of long
  half life (28 days)
• Many other things effect albumin level
• Nutritional status
• Catabolism
• Dilution
• Enhanced GI or renal loss

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Clotting Factors

• Prothrombin time
• Factors II, IV, IX and X vitamin K dependent
  coagulation factor proenzymes
• Need intact hepatic synthesis
• Adequate intestinal absorption of lipid soluble
  vitamin K
• Other things influence vit K
• Cholestatsis , nutritional deprivation
• To test for intact hepatic function give vit K

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The ABCs of Hepatitis
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Hepatitis A

• Anti-HAV IgM antibody (acute infection)
• Anti-HAV IgG antibody (immunity)

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Hepatitis B markers

• HBsAg- protein on outer envelop of virus
• HBcAb-antibody formed against the core protein
  surrounding the viral DNA
• HBeAg- structural portion of core protein
  indicative of active replication of HBV
• HBsAb-antibody directed at the surface antigen

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Hepatitis C

• Anti-HCV antibodies
• Enzyme immunoassay
• Recombinant immunoblot assay (RIBA-2)
• Detection / characterization of HCV RNA
• Qualitative reverse transcription polymerase
  chain reaction (RT-PCR)
• Quantitative test for HCV RNA level
• Genotype determination

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Viral hepatitis
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How do Patients with Liver Disease Present?

• Asymptomatic (increased transaminases)
• History and Physical examination
• Identify risk factors
• Viral markers
• Drug removal
• Imaging
• Liver biopsy

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How do Patients with Liver Disease Present?

• Jaundice
• Rapid designation of cause important
• Function problem
• Flow problem