The standing plasma test is a method used to assess lipoproteins in plasma. Which of the following best describes it?

• A. Standing plasma test
• B. Gel filtration
• C. Ultracentrifugation
• D. Electrophoresis

Answer: (A)

The standing plasma test is a simple, qualitative way to check for chylomicrons by letting plasma stand and observe separation by density. Chylomicrons are the least dense lipoproteins, so they rise to the surface and form a creamy, opaque layer. If that creamy top appears, it indicates the presence of chylomicrons in the plasma; if the plasma remains clear, chylomicrons are not present. This differs from gel filtration (separates by size), ultracentrifugation (separates by density using high-speed spinning), and electrophoresis (separates by charge and size on a gel).