Thyroid-Binding Inhibitory Immunoglobulin

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Thyroid-Binding Inhibitory Immunoglobulin

Synonym/acronym: Thyrotropin receptor antibodies, thyrotropin-binding inhibitory immunoglobulin, TBII, TRAb (TSH receptor antibodies).

Common use

To assist in diagnosing Graves’ disease related to thyroid function.

Specimen

Serum (1 mL) collected in a red-top tube.

Normal findings

(Method: Electrochemiluminescence) 0.0–1.75 units/L.

Description

There are two functional types of thyroid receptor immunoglobulins: thyroid-stimulating immunoglobulin (TSI) and thyroid-binding inhibitory immunoglobulin (TBII). TSI reacts with the receptors, activates intracellular enzymes, and promotes epithelial cell activity that operates outside the feedback regulation for thyroid-stimulating hormone (TSH) resulting in continuous production of thyroid hormones (see monograph titled “Thyroid-Stimulating Immunoglobulin”); TBII blocks the action of TSH and is believed to cause certain types of hyperthyroidism. These antibodies were formerly known as long-acting thyroid stimulators. High levels in pregnancy may have some predictive value for neonatal thyrotoxicosis: A positive result indicates that the antibodies are stimulating (TSI); a negative result indicates that the antibodies are blocking (TBII). TBII testing measures thyroid receptor immunoglobulin levels in the evaluation of thyroid disease.

This procedure is contraindicated for

    N/A

Indications

  • Evaluate suspected acute toxic goiter
  • Investigate suspected neonatal thyroid disease secondary to maternal thyroid disease
  • Monitor hyperthyroid patients at risk for relapse or remission

Potential diagnosis

Increased in

  • Evidenced by antibodies that block the action of TSH and result in hyperthyroid conditions.

  • Graves’ disease
  • Hyperthyroidism (various forms)
  • Maternal thyroid disease
  • Neonatal thyroid disease
  • Toxic goiter

Decreased in

    N/A

Critical findings

    N/A

Interfering factors

  • Lithium may cause false-positive results.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist in evaluating thyroid function.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s endocrine system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Note any recent procedures that can interfere with test results.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include albumin, antibodies antithyroglobulin, biopsy thyroid, copper, PTH, protein, RAIU, thyroglobulin, thyroid scan, TSH, TSI, T4, free T4, T3, free T3, and US thyroid.
  • Refer to the Endocrine System table at the end of the book for related tests by body system.
References in periodicals archive ?
TRAb can be detected by two approaches: in vitro assays detecting the inhibition of radiolabeled TSH to its own receptor (TBII), and biological assays measuring the functional effect (stimulatory or inhibitory) of the TRAb on the TSH-R signaling pathway.
The TSH-binding inhibitory immunoglobulin (TBII) assays traditionally used membrane extracts prepared from porcine thyroid glands, or Chinese hamster ovary cells stably transfected with recombinant human TSH-R.
In contrast, patients with dominant GD had higher fT4 (p =0.048) and higher thyroid-binding inhibitory immunoglobulin (TBII) levels.
[3] Nonstandard abbreviations: TSH, thyroid stimulating hormone; fT4, free thyroxine; TPOAb, anti-thyroid peroxidase antibodies; TRAb, TSH receptor autoantibodies; SCH, subclinical hypothyroidism; hCG, human chorionic gonadotropin; TSAb, thyroid stimulating autoantibodies; TBAb, thyroid blocking autoantibodies; TBII, TSH binding inhibition index; CHO, Chinese hamster ovary.
When measured in patients with hyperthyroidism, third-generation TRAb [also known as TSH binding inhibition index (TBII)] assays have excellent diagnostic sensitivity (97%) and specificity (99%).
Thyroid evaluation included measurement of: thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4), and serum antithyroid autoantibodies including anti-thyroid peroxidase (aTPO), thyroglobulin antibodies (aTG), thyroid-binding inhibitory immunoglobulin (TBII).
The present study showed that the sensitive TBII assay with PEG enabled the diagnosis of patients with Graves disease whose TBII could not be detected by conventional assays.
In the TBII assay, PEG may have modified the three-dimensional configuration of TSHR and enhanced the binding activity of anti-TSHR antibodies.
In samples from 24 untreated patients with Graves disease and positive TBII (group A in Fig.
To examine the effect of PEG on TBII activity, 50 [micro]L of 500 g/L PEG, 50 [micro]L of [sup.125]I-TSH, and 50 [micro]L of assay buffer were added to the mixture before the second incubation (final concentration of PEG was 100 g/L).
The TBII assay was performed as described previously (4, 6).
Detecting TSH-receptor antibodies with the recombinant TBII assay: technical and clinical evaluation.