What are the diagnostic criteria for Hepatitis A (infectious hepatitis) diagnosis?

From the Guidelines

Hepatitis A diagnosis is primarily based on detecting anti-HAV IgM antibodies in the blood, which indicate an acute infection, as serologic confirmation is required due to the inability to distinguish hepatitis A from other forms of viral hepatitis on the basis of clinical presentation alone. The diagnosis of hepatitis A involves a combination of clinical evaluation and laboratory tests, with the most direct method being the detection of anti-HAV IgM antibodies in the blood, which appear early in the disease course and typically remain detectable for 3-6 months 1. Liver function tests showing elevated liver enzymes (ALT and AST) support the diagnosis, often rising before jaundice appears. For a complete diagnosis, doctors should order both anti-HAV IgM (for current infection) and anti-HAV IgG (which indicates past infection or immunity). Patients typically present with symptoms like fatigue, nausea, abdominal pain, and jaundice, which help guide testing decisions. Some key points to consider in the diagnosis of hepatitis A include:

• The importance of serologic testing to confirm a diagnosis of acute HAV infection, as clinical or epidemiologic features alone are not sufficient 1
• The use of IgM anti-HAV testing to confirm a diagnosis, with serum IgM anti-HAV becoming detectable 5--10 days before onset of symptoms 1
• The role of total anti-HAV testing in epidemiologic studies to measure the prevalence of previous infection or by clinicians to determine whether a person with an indication for pre-exposure prophylaxis is already immune 1
• The recommendation for serologic confirmation of HAV infection in index patients by IgM anti-HAV testing before postexposure treatment of contacts 1. Given the potential for severe complications, particularly in individuals with chronic liver disease, and the importance of preventing transmission, accurate and timely diagnosis of hepatitis A is crucial, and should be based on the detection of anti-HAV IgM antibodies in the blood.

From the Research

Hepatitis A Diagnosis

• Hepatitis A is a common viral infection worldwide that is transmitted via the fecal-oral route 2.
• The diagnosis of acute infection requires the use of serologic testing for immunoglobulin M anti-hepatitis A antibodies 2, 3.
• Classic symptoms include fever, malaise, dark urine, and jaundice and are more common in older children and adults 2.
• The onset of hepatitis A is often abrupt and characteristic prodromal symptoms are followed, within a few days to a week, by dark urine and jaundice 3.
• Serum alanine and aspartate aminotransferase levels usually both rise rapidly during the prodromal period, reach peak levels and then decrease by approximately 75% per week 3.

Serological Testing

• The detection of immunoglobulin M antibody to HAV in a patient who presents with, or has recently had, clinical features of hepatitis (icteric or anicteric disease) is required for diagnosis 3.
• An avidity test for anti-HAV IgG was developed to distinguish acute infection, where low-avidity antibodies are detected, from immune reactivation 4.
• A diagnosis other than acute HA was identified in 7/11 (63.6%) of low-level reactive anti-HAV IgM results 5.
• All confirmed cases (35/35) of acute HAV were associated with at least one clinical indicator, with 28/31 cases (90%) having a documented jaundice 5.

Clinical Interpretation

• The accuracy of reports sent out to the clinician showed room for improvement, and an interpretive algorithm is proposed including a clinically significant cut-off value for anti-HAV IgM 5.
• Hepatitis A probably causes an identifiable illness in less than 5% of individuals who are infected with the virus 6.
• The disease tends to be far more symptomatic in older patients, and more than 70% of reported deaths are among persons older than 49 years of age 6.