What Is Protein-Bound Iodine Test?
Protein-sure iodine take a look at, also referred to as PBI check, laboratory check that does not directly assess thyroid function with the aid of measuring the attention of iodine to proteins circulating inside the bloodstream. Thyroid hormones are fashioned by way of the addition of iodine to the amino acid tyrosine and are usually transported within the bloodstream via carrier proteins. In the PBI test, these carrier proteins are precipitated from the blood, and the amount of bound iodine is measured. Under positive extraordinary instances, protein-sure iodine can be partly derived from iodinated materials apart from the thyroid hormones. The butanol-extraction iodine test, which kind of parallels the PBI take a look at, serves to split the thyroid hormones from different varieties of iodinated additives. Today the PBI test has been replaced by using tests able to measure thyroid hormone stages immediately. See also thyroid feature test.
Serum hormonal iodine assessments are, at great, handiest indirect indices of thyroid function. The stage of protein-bound iodine (PBI) may be stimulated by way of extrathyroidal elements, which have an effect on the metabolism of either its iodine or its protein moiety. The vulnerability of the PBI check to vitiation by way of iodine-containing tablets or iodinated radiopaque substances used in roentgenographic analysis is well known, as is the elevation of PBI in the course of being pregnant, when thyroxine-binding globulin ability is increased, and thyroxine turnover faded.
Because iodine is an critical a part of the thyroid hormone molecule, it is not surprising that dedication of the iodine content in serum become the first technique used over 6 a long time in the past for the identification and quantitation of thyroid hormone.Eleven Measurement of protein-sure iodine became the earliest technique used automatically for the estimation of thyroid hormone attention in serum. This check measured the overall amount of iodine precipitable with serum proteins, 90% of that is T4. The ordinary variety was 4 to 8 mg of iodine per deciliter of serum.
Efforts to grade serum thyroid hormone tiers with extra specificity and with lesser interference from nonhormonal iodinated compounds brought about the development of measurement of butanol-extractable iodine and T4 iodine by means of column strategies. All such chemical strategies for the measurement of thyroid hormone in serum were replaced by ligand assays, which might be without interference by means of even large quantities of nonhormonal iodine-containing materials.
The Protein-Bound Iodine (PBI) test is an older thyroid function test that measures the amount of iodine bound to proteins in the blood. It was once used to assess thyroid function, but it has largely been replaced by more accurate and sensitive tests like the TSH (Thyroid Stimulating Hormone) test, Free T4, and Free T3 tests, which provide a more comprehensive evaluation of thyroid function.
Here are some key points regarding the Protein-Bound Iodine test:
1. Diagnosis: The PBI test measures the amount of iodine bound to proteins in the blood, specifically thyroglobulin and other thyroid hormones. It was historically used to assess thyroid function and diagnose thyroid disorders such as hypothyroidism and hyperthyroidism.
a. Historical Significance: The PBI test was one of the early methods used to evaluate thyroid function, and it provided valuable information before more advanced tests became available.
b. Simple: The test is relatively simple and inexpensive, making it accessible in areas with limited healthcare resources.
c. Assessment of Thyroid Hormone Binding: The PBI test can provide information about the binding capacity of thyroid hormones to proteins in the blood. This may have been useful in understanding certain thyroid conditions in the past.
d. Research and Historical Data: While it is no longer the primary diagnostic tool for thyroid disorders, historical data from PBI tests can be valuable for research purposes and for understanding the evolution of thyroid diagnostics.
However, there are significant limitations to the PBI test:
a. Lack of Sensitivity: The PBI test is not as sensitive as modern thyroid function tests like TSH, Free T4, and Free T3. It may not detect subtle thyroid dysfunction.
b. Limited Information: The PBI test only provides information about iodine bound to proteins and doesn't give a comprehensive picture of thyroid function.
c. Inaccuracy: It can be affected by factors such as diet and medications, making it less reliable than newer thyroid function tests.
d. Not Widely Used: Due to its limitations, the PBI test is rarely used today in clinical practice. Most healthcare providers rely on more advanced and accurate tests for thyroid diagnosis.
In summary, while the Protein-Bound Iodine (PBI) test played a role in the historical assessment of thyroid function, it has largely been replaced by more accurate and sensitive tests. Healthcare providers now rely on tests like TSH, Free T4, and Free T3 to diagnose and monitor thyroid disorders because they provide more precise and comprehensive information about thyroid function. If you suspect a thyroid disorder or have concerns about your thyroid health, it's important to consult with a healthcare professional who can recommend the appropriate diagnostic tests and treatment options based on current medical standards.
Protein-bound iodine test system
(a) Identification. A protein-certain iodine take a look at a system is a device intended to produce protein-certain iodine in serum. Measurements of protein-sure iodine obtained by this tool are used inside the diagnosis and remedy of thyroid disorders.
(b) Classification. Class I (trendy controls). The device is exempt from the premarket notification methods in subpart E of component 807 of this chapter subject to the constraints in § 862.Nine.