The clinical manifestations of hepatitis vary widely according to the virus causing the disease. For HAV, the incubation period is about 15-45 days, to find evidence of virus, we can isolate the virus in the stool, and the presence of anti-HAV IgM in serology. Let’s look at hepatitis A serology.
Hepatitis A Vius (HAV) is a Picornavirus; uncoated and containing a single RNA strand encapsulated within a protein envelope. HAV has only one type of serology, but there are many different genotypes (I, II and III with subtypes A, B). Hepatitis A serology can be used to diagnose and treat hepatitis A.
What is hepatitis A virus?
Hepatitis A virus (HAV) belongs to family Picornaviridae, belongs to group Piconavirus, polyhedron (or spherical) shape with diameter 27 nm. Molecular weight of 2.5 million daltons, boxy symmetrical capsid with 20 sides is equilateral triangle so the shape is spherical, without outer cover (bare virus).
Structure of HAV is: The genome consists of a single stranded RNA, about 7500 bases long. This fiber is surrounded by a capsid consisting of 3 structural proteins (VP1, VP2 and VP3). HAV exists in very short blood so it is difficult to isolate in serology. Able to live at -250C for 6 months, at 1000C die for a few minutes.
What is the hepatitis A serology?
Hepatitis A serology is the serology containing the antibody of hepatitis A virus from a person who has had hepatitis A.
Anti-HAV antibodies appear in serology in the acute phase when overtime aminotransferase enzyme activity and virus are released in the stool.
- In the early stage: Mainly IgM
- In the recovery phase: Mainly IgG
Anti-HAV antibodies have properties that protect patients against re-infection.
Serological testing is a way of diagnosing the patient’s viral hepatitis, because all types of hepatitis have similar screening characteristics. Serological test if positive for the IgM of hepatitis A virus, then identify it as hepatitis A.
As serology GOT and GPT (or AST and ALT) levels increase, it is evident that the patient has acute viral hepatitis – a common acute infectious disease caused by hepatitis viruses (HAV, HBV, HCV, HDV, HEV, …). The disease has a common clinical feature which is a severe intoxication that causes the patient to become very tired, enlarged liver, jaundice and mucous membranes, and liver cell necrosis.
The use of hepatitis A serology in diagnosis
Diagnosis consists of 2 stages: Preliminary diagnosis (epidemiological, clinical, and subclinical) and definitive diagnosis. Serology is used in definitive diagnosis.
Two serological tests for antibodies to diagnose HAV infection are IgM (Anti HAV-IgM: Positive in serology) and total specific antibody (Anti HAV). If the test result is only positive for anti-HAV, it is not possible to distinguish between newly acquired and past infections; If Anti HAV-IgM is positive, an infected patient can be identified. Anti HAV can be used to determine immune status after vaccination.
The diagnosis is based on the viruts factor – detection of serology antigens and antibodies with anti-HAV IgM will be effective in the first four to nine weeks.
For virus isolation, serological diagnosis will use molecular biology techniques such as dot RNA hybrid blots, RT-PCR to identify RNA HAV in patient’s serology.
When determining anti-HAV, radiological immunity (RTA), enzyme-linked immunosuppression (ELISA) specifically looks for anti-HAV class IgM.
Not only does it help confirm the hepatitis A virus, the serology antibody test also helps determine the length of time that the virus has entered the body.
Diagnostic testing currently based mainly on HAV serology by ELISA technique.
Quick diagnostic tests have specificity and sensitivity vary by manufacturer: Anti-HAV total and IgM anti-HAV.
Based on serology tests by ELISA, it was found that:
- IgM Anti-HAV positive: Being infected with hepatitis A
- IgG anti-HAV positive: Immune (after about 3-12 months of IgM disappears, IgG predominates)
IgM appears 1-2 weeks after acute HAV infection and can last up to 14 weeks. IgG is present after IgM decreases and shows past HAV infection, creating immunity to re-infection; It also appears after the HAV vaccine.
In case of acute hepatitis A infection (infected not so long ago), immediately notify the local health department to take measures to prevent the spread of epidemic.
Prevention of hepatitis A virus by serology
Methods to prevent hepatitis A in general
Prevention of hepatitis includes avoiding exposure to viruses, using serology when there is a risk of exposure and vaccination.
Use serology to prevent hepatitis A
Immune globulin (ISG) is a human serology that contains antibodies to the hepatitis A virus. ISG can be used to prevent infection in people exposed to HAV. ISG works immediately after entering the body and has a protective effect for several months. ISG is often used for travelers traveling to HAV endemic areas or in close contact with people infected with hepatitis A. ISG is relatively safe, with few side effects.
Differentiate between serology and vaccine injections
- Serology injection is called passive immunization because the injected person receives antibodies from someone who has been infected with the hepatitis virus.
- Vaccination is called active immunotherapy because the virus is dead or the non-infectious component of the virus is introduced into the body to stimulate the immune system to produce antibodies.
If you intend to travel to an HAV epidemic area, you should be vaccinated at least 4 weeks before your trip because it takes several weeks for the antibodies to take effect.
And additional serology should be given alongside the vaccine if forced to go 4 weeks earlier. Globul immunotherapy works faster than vaccines but lasts shorter.
In summary, the use of serology to identify the presence of anti-HAV IgM is an important marker for early detection and observation of clinical manifestations of the disease. It is important to note, however, that hepatitis A serology should be tested early because an increase in the HAV IgM antibody level is detectable approximately three weeks after exposure, and the highest concentration can be detected after 4-6 weeks later. Within six months, IgM levels will drop to undetectable levels. At the same time, because we can use hepatitis A serology to treat illnesses, and complications are rare in hepatitis A and most infections can recover completely. So confidently treat hepatitis A virus to recover completely within 3 months, up to 6 months.