HAV IgG in Dehradun

What is a HAV IgG?

IgG antibodies against hepatitis A appear as an acute infection resolves and then persist for the rest of your life, providing durable protection against reinfection. That permanence is what makes this an immunity test rather than a diagnostic one. A positive result means you are protected, whether through an infection you had, possibly in childhood and possibly without ever noticing, or through vaccination; the test does not distinguish the two. In India a substantial proportion of adults are already immune from childhood exposure, often subclinical, because hepatitis A is milder in children and frequently passes as an ordinary stomach upset. That prior immunity is precisely why testing before vaccination can be worthwhile: someone already protected gains nothing from the vaccine. Conversely, improving sanitation means a growing number of Indian adults reach adulthood without exposure, and adults who then catch hepatitis A tend to have a considerably more severe illness than children do. The corollary matters: a negative IgG in an adult is not merely a neutral finding, it identifies someone who would benefit from vaccination.

Why take this test?

HAV IgG is advised when the question is protection rather than illness: before vaccination, to avoid immunising someone already immune; before travel to an area where hepatitis A is common, if vaccination status is unknown; and for people with chronic liver disease from any cause, including hepatitis B or C, fatty liver or cirrhosis, in whom a superimposed hepatitis A infection can be much more dangerous and for whom vaccination is specifically recommended. It is also used in outbreak settings to identify who is susceptible, and occasionally to confirm a vaccine has taken. It is not the test for someone who is acutely unwell with jaundice; HAV IgM answers that question, and ordering IgG in an acute illness produces a positive result that says nothing about the current episode.

• Checking immunity before hepatitis A vaccination
• Before travel where vaccination status is unknown
• Chronic liver disease of any cause, where superinfection is dangerous
• Identifying susceptible people during an outbreak
• Confirming response to vaccination
• Not the right test for acute jaundice — use HAV IgM

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