A quantitative test is one that?

A quantitative test specifically measures the amount of a substance in a sample rather than just indicating whether the substance is present or not. This makes it essential for assessing levels of substances, such as hormones or drugs, in various medical contexts. The correct answer encompasses both aspects: determining not only if a substance exists but also quantifying how much of it is present. This is crucial in clinical settings, as understanding the concentration of a substance can guide diagnosis, treatment decisions, and monitoring of therapies.

The other options focus on limited functions. For instance, testing for only the presence of a substance would be a qualitative analysis and does not provide the detailed numeric data required for effective treatment plans. Similarly, testing solely for the amount of a substance ignores the dimension of presence, which is insufficient for a thorough understanding of a patient's condition. Tests that evaluate qualitative reactions alone do not provide the quantitative insights needed in many clinical situations. Therefore, the comprehensive nature of a quantitative test makes it vital in a clinical setting.