If an automated hemoglobin test shows a value of 15g/dl, what is the expected hematocrit value?

When interpreting hemoglobin and hematocrit values, it's important to understand the relationship between the two. A commonly accepted rule of thumb is that the hematocrit value is approximately three times the hemoglobin value, known as the "rule of three." This means that if a hemoglobin level is 15 g/dL, the expected hematocrit would be around 45%.

This relationship arises because hemoglobin (which is the protein in red blood cells that carries oxygen) constitutes a significant portion of the volume of red blood cells. As such, when hemoglobin levels are measured, they can be used to estimate hematocrit levels quite reliably.

In this case, with a hemoglobin level of 15 g/dL, applying the rule of three gives us a hematocrit value of 45%, matching the correct answer. This guideline provides a useful way to quickly assess and cross-check blood characteristics in clinical practice, making it a valuable tool for medical assistants when interpreting lab results.