At onset, the various human hepatitis viruses cause very similar illnesses. Therefore, neither patient nor doctor can tell by symptoms or signs if a given individual is suffering from Hepatitis A. Fortunately, we now have excellent blood tests, widely available, to accurately diagnose Hepatitis A. These are tests for antibodies, i.e. the patient’s immune response to Hepatitis A proteins, the capsid proteins. Antibodies of the IgM variety, which indicated acute disease, and antibodies of the IgG variety, which stay positive for life, should both be measured. Following is the interpretation of the results:
– IgM negative / IgG negative: Most persons with these results have never contracted Hepatitis A. Antibodies of the IgM variety develop 5 — 10 days prior to the onset of symptoms.
– IgM positive / IgG negative: This result indicates acute Hepatitis A.
– IgM positive / IgG positive: This result indicates that acute Hepatitis A occurred within the last 6 months. By 6 months, the IgM reverts to negative.
– IgM negative / IgG positive: The person with this result is immune to Hepatitis A. They have either been infected with the virus months or years in the past (with or without symptoms), or they have been vaccinated for Hepatitis A. However, if they are currently ill, it is not likely to be due to Hepatitis A.
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