Final answer:
Tests for hepatitis B can indicate previous infection and now immunity through the detection of specific antibodies in the patient's serum.
Step-by-step explanation:
Tests for hepatitis B (HBV) infection can indicate previous infection and now immunity through the detection of specific antibodies in the patient's serum.
One such test is the Hepatitis B surface antibody (anti-HBs) test. If the test detects the presence of anti-HBs antibodies, it indicates that the patient has been previously infected with HBV and now has immunity against the virus.
Another test is the Hepatitis B core antibody (anti-HBc) test. If the test detects the presence of anti-HBc antibodies, it indicates a previous or ongoing HBV infection, even if the patient appears to have recovered.