A 1-year-old girl with hyperlipoproteinemia and lipase deficiency has a sample refrigerated overnight. The serum would most likely appear as which of the following?

• A. Clear
• B. Cloudy
• C. Creamy layer over cloudy serum
• D. Creamy layer over clear serum

Answer: (D)

Chylomicronemia creates a distinct physical appearance in refrigerated serum. When lipase is deficient, chylomicrons—big, triglyceride-rich lipoproteins produced from dietary fats—aren’t cleared from the blood. They rise to the top of the sample and form a creamy layer, while the rest of the serum remains clear. Refrigeration enhances this separation, so you see a creamy layer over clear serum.

That’s why the expected finding is a creamy layer atop clear serum. If the lipemia were due to VLDL or other lipoproteins without chylomicrons, the serum would be uniformly turbid rather than having a separate cream layer.