Diagnosis of Viral Hepatitis

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Análisis de sangre hígado

Blood test. The hepatitis viruses can be detected by means of a simple blood test. When an individual enters into contact with a hepatitis virus the immune system responds by producing antibodies. If a person already has antibodies for a given hepatitis virus, it indicates that they have been in contact with the virus at some time in their life. There are IgG antibodies, indicative of chronic or past infection, and IgM antibodies, which indicate acute or recent infection.

The blood test also reveals information about the condition of the liver. Transaminases are proteins found inside liver cells (hepatocytes). There are two different types of transaminase, AST and ALT (also known as GOT and GPT, respectively). Transaminase levels provide information about the degree of liver inflammation and the destruction of liver cells; however, low or normal values do not rule out the possibility of liver disease, while very high values are not necessarily an indication of advanced disease.

In addition to transaminases, the blood test analyses other parameters that could help determine the severity of any liver damage.

  • Total bilirubin. Bilirubin is produced by the liver and eliminated in bile. Its accumulation results in a high value in the test and it is responsible for the yellow discolouration of the skin characteristic of liver diseases (jaundice). This parameter is often high in cases of acute hepatitis caused by hepatitis A, B or E viruses.
  • Albumin. This is the main protein found in blood and has several functions. It is produced by the liver and low blood levels indicate poor liver function.
  • Prothrombin time. This is a laboratory test that measures the blood’s coagulation capacity. The proteins associated with blood coagulation are produced in the liver. If the liver is functioning poorly due to acute or chronic damage, it may result in a lack of these proteins which could alter blood coagulation and therefore the blood takes longer to clot. In the case of acute hepatitis, an altered prothrombin time shows the condition is severe and that there is liver failure.
  • A complete blood count examines the different types of blood cell: erythrocytes (red blood cells), leucocytes (white blood cells) and platelets. This test also helps identify alterations associated with liver disease, especially in cases of advanced liver disease, such as cirrhosis, where there is typically a low level of erythrocytes (anaemia), leucocytes or platelets.
Análisis de sangre de detección de ADN o ARN viral

Viral DNA or RNA detection. The presence of the virus can be confirmed with another blood test called polymerase chain reaction (PCR). PCR is a technique used to identify the genetic material, DNA or RNA, of a given organism. PCR can detect the RNA of hepatitis C, A and E viruses and the DNA of hepatitis B from a blood sample and it is the most effective analytical method for detecting an active hepatitis virus infection. If viral RNA or DNA are detected, the test result is positive; if they are not detected, the result is negative.

Prueba para medir las cicatrices o fibrosis del hígado, biopsia hepática

Measuring liver fibrosis. Liver fibrosis is the accumulation of scar tissue due to the chronic damage caused by liver diseases. Various analytical parameters and complementary tests are combined to assess the extent of liver fibrosis:

  • Liver biopsy. A small piece of liver tissue is collected using a needle. It is an invasive but safe technique with a low risk of complications.
  • Transient elastography (TE) or Fibroscan® quantifies liver elasticity, which is inversely proportional to the degree of liver fibrosis. It is a painless technique carried out using ultrasound, it provides an instant result and can be repeated safely on a regular basis.
ultrasound measurement

Abdominal ultrasound. This is an imaging technique based on ultrasound technology. It provides a view of the liver and surrounding structures in function of their density, such as liver cysts, liver tumours and gallbladder or bile duct stones, and can be used to assess the size of and blood flow through the hepatic portal vein and arteries, the overall size of the liver and whether it has a uniform shape. It is a totally painless technique and harmless for the patient.

Persona con tubo boca hasta el estómago, endoscopia digestiva

Gastrointestinal endoscopy. Esophagogastroduodenoscopy (EGD) or upper gastrointestinal endoscopy is indicated in patients with advanced liver disease to rule out the presence of oesophageal varices, which would denote that the patient has cirrhosis and portal hypertension. If the patient has large oesophageal varices, there is a risk they could rupture and cause potentially severe upper gastrointestinal bleeding. This risk can be reduced if suitable prophylactic treatment with beta-blockers is established.

Substantiated information by:

Concepció Bartrés
Sergio Rodríguez-Tajes
Xavier Forns
Zoe Mariño

Published: 20 September 2018
Updated: 20 September 2018

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