Question

Rapid bedside detection of HBsAg in point-of-care kits is based on which principle?

• A. Immunochromatography assays
• B. Chemiluminescence
• C. ELISA
• D. Immunofluorescence

Hint:

Think of the simple lateral-flow card strip used at the bedside, not a lab machine.

Answer 1

The Correct Option is A

Clinical pearl approach: Whenever a question says rapid, point-of-care or card test for an antigen or antibody, the default answer is the lateral-flow immunochromatographic assay. That is exactly how the bedside HBsAg strip behaves.
How it works: Serum is dropped on the pad and wicks along the membrane. Mobile gold or dye-labelled anti-HBs picks up any HBsAg, and the complex is trapped at a fixed test line, producing a coloured band you read by eye in minutes. No instrument is needed.
Eliminating the rest: Chemiluminescence and ELISA are plate or analyser based methods used in the lab for confirmation and quantitation, not the strip principle. Immunofluorescence needs a microscope and labelled antibody and is not the screening method for HBsAg.
Hence the principle is immunochromatography. Ref: Jawetz, 27e, p.504.