What does the term "occult" refer to in a medical context?

In a medical context, the term "occult" refers to something that is hidden or concealed. This term is often used to describe conditions or substances that are not immediately visible or detectable through standard examinations or tests. An example of this usage is "occult blood," which refers to blood that is present but not visible to the naked eye, often requiring special tests to detect.

The other options refer to characteristics that are opposite to "occult." For instance, visible and detectable conditions can be easily identified without further investigation, commonly observed suggests that something is frequently seen, and clear and apparent describes something that is straightforward and obvious. In contrast, "occult" specifically implies a level of obscurity that necessitates further inquiry to uncover what is hidden.