Serum/plasma mass concentration of protein-bound iodine (PBI)

What Is Protein-Bound Iodine (PBI) Used For?

PBI is primarily used to evaluate thyroid function, particularly in diagnosing or monitoring conditions related to iodine deficiency or thyroid hormone synthesis. It can also be part of older thyroid function testing protocols, though newer methods like free thyroxine (T4) or thyroid-stimulating hormone (TSH) tests are often preferred today.

How Is PBI Tested?

This test involves drawing blood from a vein. The blood sample is then processed to separate the protein-bound iodine from other components. The iodine bound to proteins is measured using a specialized laboratory technique, often involving chemical analysis to determine its concentration.

What Does a PBI Test Result Mean?

Results from a PBI test indicate the total iodine bound to proteins in your blood. While this test can provide insight into thyroid function and iodine status, it is less commonly used today compared to more direct thyroid hormone tests. Interpretation requires clinical correlation with patient symptoms and other diagnostic findings.

When Might You Need a PBI Test?

A PBI test may be ordered in specific cases where iodine levels or thyroid function are suspected to be abnormal, such as in patients with suspected iodine deficiency, thyroid nodules, or those undergoing evaluation for thyroid disorders. It may also be used historically in certain diagnostic workflows or research settings.