Laboratory diagnosis of Viral Hepatitis

Viral infections of the liver are serious diseases caused by several unrelated viruses. These diseases resemble each other and can only be differentiated with the aid of laboratory tests.

Aetiology of hepatitis:

Causes of hepatitis can be divided into non infectious causes and infectious causes as follows:

A. Non-infectious causes

1.      Biliary obstruction

2.      Primary biliary cirrhosis

3.      Drug toxicity

4.      Drug hypersensitivity

B. Infectious causes

1.      Bacteria – Leptospira, Tubercle bacilli, Treponema etc

2.      Parasites – Entamoeba, Toxoplasma

3.      Viruses:

a.      Hepatitis A virus, Hepatitis B virus, Hepatitis C virus,         Hepatitis D virus, Hepatitis E virus

b.      Rubella virus

c.      Adenovirus

d.      Enterovirus (Coxsackie B)

e.      Cytomegalovirus

f.       Herpes simplex virus

g.      Infectious mononucleosis

h.      Epstein Barr virus

i.       Varicella zoster virus

Viral hepatitis is an inflammatory disease of the liver caused by an infection with hepatitis viruses. In these cases liver is the main target organ and among most of the cases is the only known site of replication of virus.

Hepatitis A and E

• These are transmitted by feco-oral route. Incubation period 2-6 weeks.
• The clinical disease consists of two stages – the prodromal or pre-icteric and the icteric stages. 
• Onset may be acute or insidious with fever, malaise, anorexia, nausea, vomiting and liver tenderness. 
• These usually subside with onset of jaundice. Recovery is slow, over a period of 4-6 weeks.

Hepatitis B, C and D

• These are transmitted  by parenteral, sexual and perinatal routes.
• Hepatitis B is the most wide spread of viral hepatitis. 
• The incubation period is about 1-6 months. Clinical picture is similar to that of Hepatitis A but it tends to be more severe and protracted.
• Extrahepatic complications like arthralgia, urticaria and rarely polyarteritis or glomerulonephritis may occur. 
• They are ascribed to circulating immune complexes containing the viral surface antigen. A portion of the cases may progress to chronic stage. 
• A few may develop hepatocellular carcinoma after several decades. The course of Hepatitis C is more chronic in nature. 
• The hepatitis D virus is known to cause super-infection or Co-infection with hepatitis B viral infections & tends to be more severe infection.

Laboratory diagnosis:

Following parameters are used for confirmation of diagnosis of hepatitis

A         Biochemical changes – elevated serum bilirubin, SGPT and globulin; & relative fall in albumin.

B         Haematological changes – leucopenia with large number of atypical lymphocytes

            Detection of following serological markers are used for diagnosis of specific viral aetiology.

1.      Hepatitis A: Anti-HAV antibody

2.      Hepatitis B:

-        Hepatitis B surface antigen – HBsAg

-        Anti hepatitis B surface antigen –  Anti HBsAg

-        Anti Hepatitis B core antigen – Anti HBcAg

-        Hepatitis B envelop antigen – HBeAg

-        Anti Hepatitis B envelop antigen –Anti HBeAg

-        HBV DNA

3.      Hepatitis C: Anti-HCV antibody, HCV RNA

4.      Hepatitis D: Delta antigen / Anti-HDV antibody

5.      Hepatitis E: Anti-HEV antibody

 

Ø  The serological markers are detected by ELISA / CLIA / Immunochromatography methods

Ø  The viral DNA / RNA can be detected by PCR technology