Lewis test

The Welsh cardiologist Sir Thomas Lewis (1881–1945) was the first to describe the test named after him (Antwerpes 2025).

The Lewis test is a simple method for distinguishing between central and peripheral cyanosis (Antwerpes 2025).

• Indications:

The test can be used in cases of cyanosis to determine whether it is central or peripheral cyanosis (Antwerpes 2025).

• Test Procedure:

The subject’s earlobe is massaged until a capillary pulse appears (Herold 2025). After the earlobe has been massaged until it is completely devoid of blood, capillary blood flows in (Pschyrembel online).

• Test result:

In the case of peripheral cyanosis, the cyanotic discoloration disappears briefly; in the case of central cyanosis, however, the discoloration remains (Herold 2025)

• Central cyanosis:

In central cyanosis, the returning blood is deoxygenated, causing the earlobe to remain bluish in color (Antwerpes 2025).

• Peripheral cyanosis:

In peripheral cyanosis, oxygenated blood initially flows in, causing a brief reddening of the earlobe (Antwerpes 2025).

1. Antwerpes F et al. (2025) Lewis Test. DocCheck Flexikon https://flexikon.doccheck.com/de/Lewis-Test
2. Herold G et al. (2025) Internal Medicine. Herold Verlag 153
3. Kasper D L, Fauci A S, Hauser S L, Longo D L, Jameson J L, Loscalzo J et al. (2015) Harrison’s Principles of Internal Medicine. McGraw-Hill Education
4. Pschyrembel Online (2025) Lewis Test. https://www.pschyrembel.de/Lewis-Test/Z04QA/doc/