PBI testing, or protein-bound iodine testing, is a formerly used test to evaluate thyroid function.
Understanding PBI Testing
This test involves measuring the amount of iodine bound to proteins in your blood serum. This measurement provides an estimate of the thyroid hormone that is attached to proteins as they circulate in your peripheral blood. As stated in the reference, it was formerly used, and it's important to understand its historical context.
Key Aspects of PBI Testing:
- Measurement: The test measured iodine that is attached to proteins in the blood.
- Thyroid Function: The PBI test was primarily used to indirectly gauge the function of the thyroid gland.
- Historical Use: PBI testing is no longer a common practice; it has been replaced with more accurate tests. The reference indicates the test was last updated May 29th, 2023, which highlights how long ago this test was a main test for thyroid function.
How it Worked
The underlying principle was that thyroid hormones, such as thyroxine (T4) and triiodothyronine (T3), circulate in the bloodstream primarily bound to proteins. Thus, measuring the iodine bound to these proteins was thought to provide an indication of circulating thyroid hormones.
Why It's Not Used Anymore
PBI testing has been largely replaced by more direct and reliable methods, including:
- T4 and T3 Assays: Direct measurements of thyroid hormone levels in the blood are now standard practice.
- TSH Tests: The thyroid-stimulating hormone (TSH) test is more sensitive and specific for thyroid function.
Table Summarizing PBI Testing
| Feature | Description |
|---|---|
| Test Name | Protein-bound iodine test (PBI) |
| Purpose | Formerly used to assess thyroid function by measuring iodine bound to proteins. |
| Measurement | Amount of iodine attached to proteins in blood serum. |
| Current Usage | Largely obsolete; replaced by more accurate T4, T3, and TSH tests. |
| Last Updated | May 29th, 2023 (per reference) |
Conclusion
PBI testing, while once a tool for thyroid function assessment, is no longer in mainstream clinical use. More accurate and direct methods are now preferred.
