Fridge test

The refrigerator test is a laboratory medical examination procedure (Antwerpes 2023) for the detection of chylomicrons in blood serum (Herold 2025).

The orienting classification according to Fredrickson differentiates between:

• Normal serum: no creaming
• Type I: The serum is milky-cloudy, there is creaming, the background is clear
• Type IIa: clear (indicating that only LDL is elevated)
• Type II b: clear or cloudy (indicating that VLDL or remnants [lipoproteins] are elevated)
• Type III: cloudy (indicating that VLDL or remnants are elevated)
• Type IV: cloudy / milky (indicating that VLDL or remnants are elevated)
• Type V: milky, creaming, the dugout is cloudy (Gressner 2017 / March 2023)

The refrigerator test can provide indications of pathological blood lipid levels. However, the sensitivity is low (Antwerpes 2023).

- Indications:

Presence of a lipid metabolism disorder (Antwerpes 2023)

- Procedure:

The patient must have fasted for 12 hours before the blood sample is taken. The serum is then stored in the refrigerator at 4-8° (Antwerpes 2023 / Gressner 2017). After 24 h at the latest, the chylomicrons settle as a cream layer (Herold 2025).

- Evaluation:

• Clear serum: normal concentration of triglycerides
• Cloudy serum: the concentration of triglycerides or cholesterol is increased
• Framed serum: detection of chylomicrons (Gressner 2017)

In the case of repeated pathological results, a differentiated analysis of the lipid metabolism is recommended, e.g. by ultracentrifugation (Gressner 2017).

1. Antwerpes F et al. (2023) Refrigerator test. DocCheck Flexikon. Doi: https://flexikon.doccheck.com/en/K%C3%BChlschranktest
2. Gressner A M, Gressner O A (2017) Refrigerator test. Doi: https://www.springermedizin.de/emedpedia/detail/lexikon-der-medizinischen-laboratoriumsdiagnostik/kuehlschranktest?epediaDoi=10.1007%2F978-3-662-49054-9_1792
3. Herold G et al (2025) Internal medicine. Herold publishing house 711
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