Liver function tests (LFTs) encompass a battery of assessments to quantify proteins, enzymes, and bilirubin levels within the bloodstream. These tests serve as diagnostic tools for identifying liver infections, diseases, or damage. Deviations, whether elevated or reduced, in the concentrations of these substances may indicate an underlying liver ailment. The substances analyzed in LFTs are as follows:
- Gamma Glutamyltransferase (GGT): An enzyme present in the circulatory system.
- Alkaline Phosphatase (ALP): This is an enzyme present in the liver and bone.
- Aspartate Transaminase (AST): An enzyme present in both the liver and muscles.
- Alanine Transaminase (ALT): An enzyme predominantly present in the liver.
- Lactate Dehydrogenase: Another enzyme synthesized by the liver, ubiquitously distributed in the body’s cells.
- Albumin and Total Protein: Albumin is an essential protein facilitating immune defense and various bodily functions. Total protein testing evaluates the collective levels of albumin and other proteins in the blood.
- Bilirubin: A byproduct resulting from the breakdown of red blood cells.
- Prothrombin Time (PT): A test measuring the duration required for blood clotting.
Purpose of Liver Function Tests
Liver function tests play a vital role in the diagnosis and treatment of the following conditions:
- Detection of liver infections, such as hepatitis.
- Monitoring of medication side effects affecting liver function.
- Evaluation of the severity of diseases like cirrhosis.
- Assessment of the effectiveness of liver disease treatment.
Indications for Liver Function Tests
Liver function tests are recommended if an individual experiences symptoms associated with liver disease, including:
- Nausea and vomiting
- Dark urine and pale stools
- Abdominal pain
- Pruritus (itching)
- Abdominal swelling
- Loss of appetite
Additionally, individuals with certain risk factors should undergo liver function tests.
These factors include:
- Suspected exposure to hepatitis viruses.
- Presence of alcohol use disorder (chronic alcohol addiction).
- Use of medications known to impact liver function and potentially cause damage.
- Family history of liver conditions.
Procedure for Liver Function Tests
Typically, a blood sample is obtained from a vein in the patient’s arm. Some bruising or soreness at the puncture site may occur. A tiny needle is inserted into the vein to collect a small amount of blood into a tube attached to the needle. Minimal temporary discomfort may be experienced during needle insertion and removal. The blood sample is subsequently delivered to a lab for evaluation. The procedure only takes a few minutes.
Interpretation of Test Results
ALT Test Results: Elevated ALT levels indicate improper liver function or damage. Further testing and evaluation are recommended if the ALT level exceeds 33 IU/L for males and 25 IU/L for females.
AST Test Results: Increased AST levels suggest liver or muscle damage.
ALP Test Results: High ALP levels may indicate bone disease, bile duct obstruction, or liver inflammation. Children, adolescents, and pregnant women naturally have elevated ALP levels.
Albumin Test Results: Below-normal albumin levels signify impaired liver function. Kidney disease, malnutrition, kidney inflammation, and infection can cause a decrease in albumin levels.
Bilirubin Test Results: Typically, the liver efficiently processes bilirubin. However, impaired liver function can hinder proper processing, leading to elevated levels in the blood. High bilirubin levels in your LFT test results indicate inadequate liver function.
Lactate Dehydrogenase (LD) Test Results: Elevated LD levels can suggest liver damage, but other disorders can also contribute to elevated enzyme levels.
Prothrombin Time: Prolonged prothrombin time may indicate liver damage, deficiencies in coagulation factors, or vitamin K deficiency. Additionally, it can be elevated due to the use of blood-thinning medications.
Diagnosis and Next Steps: Test results alone do not provide a definitive diagnosis, but they guide further action. If liver dysfunction is indicated, your doctor will review your medical history and medications to identify the cause. Additional tests may include evaluating for liver infections or diseases through imaging tests like CT scans or ultrasounds. A liver biopsy may be recommended in some cases to assess conditions such as fatty liver, fibrosis, or other liver-related ailments.
Pointers To Frequently Asked Questions
- Significance of Elevated Gamma Glutamyltransferase (GGT) Levels: Elevated GGT levels may indicate bile duct or liver damage. Higher GGT levels are commonly observed in individuals taking medications metabolized by the liver or those who consume alcohol.
- Liver Function Test Abnormalities without Liver Disease: Yes, temporary conditions like muscle trauma, burns, shock, severe infections, hemolysis, pregnancy, dehydration, or pancreatitis can result in abnormal liver function test results.
- Importance of Family Medical History: Inherited liver conditions such as Wilson’s disease (copper accumulation in organs) and hemochromatosis (iron buildup in the body) emphasize the significance of timely diagnosis and treatment.
- Follow-up Tests for Abnormal Liver Function Tests: Based on the results and considering family history, symptoms, and signs, your doctor may order further tests to investigate the underlying cause. Suspected viral infections may prompt hepatitis A, B, or C tests. For hepatitis, an ethanol test might be required, while Wilson’s disease may necessitate a ceruloplasmin test.
- Preparations before Liver Function Tests: To ensure accurate results, your doctor may advise avoiding certain foods and medications before the blood draw, as they can influence liver function test results.
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