NHA Phlebotomy Certification Practice Exam

Which test result can be impacted by iodine used for site cleaning?

1. Sodium

2. Potassium

3. Calcium

4. Chloride

The correct answer is: Potassium

Iodine solutions are commonly used for skin antisepsis before blood draws to prevent infection. However, the use of iodine can lead to alterations in the levels of certain substances in the blood. Specifically, when iodine is used on the skin and then blood is drawn, it can result in false elevations in potassium levels. This occurs because iodine can interfere with the potassium measurement process in laboratory tests. When blood is collected after using iodine for site cleaning, it has the potential to cause a phenomenon known as pseudohyperkalemia, where the potassium measurements are inaccurately high due to external contamination or the effect of the iodine. This is particularly notable in patients with compromised cellular integrity or conditions that release potassium from cells into the bloodstream. As a result, potassium levels may appear artificially elevated when they are actually within normal limits. In contrast, other electrolytes like sodium, calcium, and chloride are generally not affected by the presence of iodine during sample collection and testing in the same manner. Thus, it's essential for phlebotomists and laboratory personnel to be aware of these potential interferences and to choose appropriate site cleaning methods when preparing for blood draws, particularly for potassium testing.