Interpretation and Clinical Application of Liver Function Indicators
Liver function is a very important clinical indicator, but there are often some problems in clinical evaluation, such as some patients simply have elevated “transaminase levels” and are simply considered to have “abnormal liver function”. In fact, the indicators reflecting liver function should include the synthesis, excretion, metabolism of drugs, immunity and other functions of the liver, not just the level of transaminases. Li Yuerong, Department of Infectious Diseases, Zhangqiu People’s Hospital
Classification of liver function and examination items
Basic functions
Synthesis Alb, PT, lipids and lipoproteins
Excretion Bilirubin, bile acids, pigments (sodium sulfobromophthalein, indocyanine green) excretion
Metabolism Aminopyrine, finasteride, tryptophan, urea, etc. metabolism
Immunity Gamma-globulin
Markers
Hepatocellular injury – Enzymatic changes: ALT, AST, LDH, adenosine deaminate
Cholestasis Bilirubin, bile acids, cholesterol, ALP, GGT
Cirrhosis Type III, VI, I, IV collagen, hyaluronic acid, proline hydroxylase
Hepatocellular carcinoma AFP, GGT-II, AFU, AKP-Ⅰ, aldolase A, decarboxylated thrombin
Autoimmune hepatitis Smooth muscle antibody
Primary biliary cirrhosis Mitochondrial antibodies, IgM
I. Synthetic functions of the liver
(I) Albumin (Alb)
The liver is the only place where albumin is synthesized, and serum albumin level is one of the good indicators of chronic liver injury. Decreased serum albumin level is seen in: insufficient nutritional intake, impaired synthesis, excessive consumption and increased loss. The serum albumin level in patients with chronic liver disease can reflect the ability of the liver to synthesize albumin and changes in the volumetric distribution of albumin, and if the serum albumin level is reduced and not easily recovered, the prognosis is often poor.
(ii) Prothrombin time
In hepatic impairment, the associated impaired synthesis of coagulation factors can lead to prolonged PT, which is one of the early predictors of abnormal liver function. prolonged PT and uncorrectable vitamin K predicts extremely poor liver function. In fulminant liver failure, PT is an important early diagnostic indicator.
(iii) Lipids and lipoproteins
Lipids and lipoproteins are not sensitive indicators of liver damage, but serum cholesterol ester levels decrease in response to hepatocellular damage and are proportional to the degree of liver damage. In chronic liver disease, lipoproteins are reduced and their levels are negatively correlated with transaminases and bilirubin.
Excretory function of the liver
(A) Bilirubin
Bilirubin is one of the important indicators of liver function. The normal level of total bilirubin TBIL is <1.1mg/dl (17.1μmol/l), 70% of which is indirect bilirubin, which cannot be filtered from the kidney. Only direct bilirubin can be excreted from the urine. Note: 1. TBIL < 5 times normal (85 μmol/l) in hemolytic jaundice when liver function is normal. 2. TBIL < 500 μmol/l in jaundice of any cause when renal function is normal. 3. The presence of jaundice, but negative urinary bilirubin, indicates elevated indirect bilirubin. 4. Many jaundices with predominantly elevated indirect bilirubin alone are Gilbert syndrome, this syndrome has no pathological tissue changes in the liver tissue, has no significant effect on the organism, and generally requires no special treatment.
III. Serum enzymatic levels
(I) ALT, AST
The specificity of ALT is better than AST.
1. When ALT > 10 times normal, there is definitely liver damage (such as chronic hepatitis B)
2. when ALT and AST are elevated in biliary tract disease, but <8 times normal
3. ratio of AST/ALT: (1) estimate the degree of liver damage: the greater, the more serious the damage; (2) identify liver disease: alcoholic liver > 2, slow hepatitis B > 1 may have liver fibrosis or cirrhosis
(B) Alkaline phosphatase ALP
1. ALP>4 times normal: cholestasis syndrome
2. ALP>2.5 times normal, ALT, AST<8 times normal: 90% cholestasis
3. ALP>2.5 times normal, ALT, AST>8 times normal: 90% of viral hepatitis
(C) Glutamyl transpeptidase GGT
90% of patients with hepatobiliary disease have elevated GGT, GGT>10 times normal, mostly from on alcoholic liver, intrahepatic and extrahepatic biliary sludge, primary liver cancer
IV. Evaluation of liver enzymatic indexes
1. A survey of a large sample of healthy people in the UK found that 6% of the asymptomatic normal population had elevated ALT and AST, and 5% of the normal population had all test results outside the “normal value” range. Therefore, some abnormal liver test results are not really abnormal.
2. The treatment of elevated single transaminase level is: check once, if the elevation is more than 2 times the normal, further examination is needed.
V. Interpretation of hepatitis B two pairs of half
Major triple-positive Minor triple-positive
HBsAg（+） HBsAg（+）
HBeAg（＋） HBeAb（＋）
HBcAb（＋） HBcAb（＋）
Single HBsAg (+) is a hepatitis B carrier
Hepatitis B two-to-half results and clinical significance
HBsAg HBsAb HBeAg HBeAb HBcAb Clinical significance
1 + – – – + (major triple positive) acute and chronic hepatitis, HBV replication stage
2 + – – – + Acute HBV infection, chronic HBsAg carriers, weakly infectious
3 + – – – + + Acute HBV tends to recover, chronic HBsAg, long-term persistent susceptible to cancer (small triplet)
4 – – – – – Not infected with HBV
5 – + – – + Pre-existing infection with immunity Atypical recovery, acute HBV infection
6 – – – + + Previous HBV infection, acute HBV recovery, few still infectious
7 – – – – + Pre-existing HBV infection, acute HBV window
8 – + – – – Passive or active HBV immunization, recovered from infection
9 – + – + + – Previous HBV infection, acute HBV recovery
10 + – – – – Chronic HBV carrier, acute HBV infection
11 + – – + – Chronic carrier, acute HBV infection tending to recover
12 + – + – – Early infection, highly infectious
13 + – + + + + Acute HBV infection tending to recover, chronic HBsAg carrier
14 + + – – – -/+ Early stage of subclinical HBV infection, secondary infection with different subtypes of HBV
15 + + + + – + Subclinical type or atypical infection
VI. Key points
1. elevated unconjugated bilirubin alone is likely to be Gilbert’s syndrome.
2. persistent elevated transaminase levels with negative viral indicators and no alcohol consumption may be fatty liver or non-alcoholic fatty liver hepatitis.
3. In acute fulminant liver failure, PT is an important early diagnostic indicator.
4. In patients with abnormal transaminases and jaundice, the possibility of pharmacologic liver disease should not be overlooked. In patients on drug therapy, weekly follow-up is required when ALT levels are less than 3 times the normal upper line, and it is best to discontinue drugs when greater than 3 times.
5. When the liver function index is abnormal, do not blindly take medication to correct it, but go to a specialist hospital for consultation. Because the drugs for liver disease have certain indications and are expensive, and there is individual variability in specificity, there is still no specific and absolutely effective drug.