For screening of hepatitis-B, most commonly used test is –
**Core Concept**
The most commonly used test for screening of hepatitis-B involves detecting the presence of antibodies or antigens in the blood that are specific to the hepatitis-B virus (HBV). This test is crucial for early detection, diagnosis, and management of HBV infection.
**Why the Correct Answer is Right**
The correct answer is the enzyme-linked immunosorbent assay (ELISA), which is a sensitive and specific test for detecting hepatitis-B surface antigen (HBsAg) in the blood. HBsAg is a protein on the surface of the HBV particle and is the first detectable marker of infection. ELISA detects the presence of HBsAg antibodies, which are produced in response to HBsAg. This test is widely used for screening due to its high sensitivity and specificity.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a test for hepatitis-B screening. The term "hepatitis-B test" is too broad and does not refer to a specific diagnostic tool.
**Option B:** This option is incorrect because although the rapid diagnostic test (RDT) is used for screening, it is not the most commonly used test for hepatitis-B. RDTs are less sensitive and specific compared to ELISA.
**Option C:** This option is incorrect because the complement fixation test (CFT) is not commonly used for hepatitis-B screening. CFT is an older immunological technique that is less specific and sensitive compared to ELISA.
**Clinical Pearl / High-Yield Fact**
The window period for hepatitis-B screening is the time between the onset of infection and the appearance of detectable HBsAg in the blood. This period can range from 1-4 months, making it essential to repeat screening tests if initial results are negative.
**Correct Answer: A. ELISA**