Thyroid-stimulating Immunoglobulin (TSI)

Casandra

Casandra Test Code LC87878Version 1 (DRAFT)

Performing Lab

Lab LabcorpLab Test ID 140749CPT Code 84445

Thyroid-stimulating Immunoglobulin (TSI)

Also known as: Human Thyroid Stimulator (HTS), Long-acting Thyroid Stimulator (LATS)

Clinical Use

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Use

The measurement of thyroid stimulating autoantibodies, in conjunction with other clinical and laboratory findings, is used as an aid in the diagnosis of patients suspected of having Graves' disease.1

Special Instructions

For diagnostic purposes, the results obtained from this assay should be used in combination with the clinical examination, patient medical history, and other findings. Prepare a sterile venipuncture site. Serum or plasma must be separated from blood cells by centrifugation, ideally within two hours of collection. If using a red-top tube or plasma, transfer the separated serum or plasma to a plastic transport tube.

Limitations

Heterophilic antibodies in human serum can react with the immunoglobulins included in the assay components, causing interference with in vitro immunoassays. Commonly used Thyrotropin Receptor Autoantibody assays do not distinguish between TSI and Thyroid Blocking Immunoglobulins (TBI). In the validation for FDA submission, TSI values for patients with other thyroid or autoimmune diseases had an upper limit of 0.39 IU/L. Discrepancy may occur in patients undergoing treatment.

Test Details

Methodology

Immunoassay (CLIA)

Biomarkers

Thyroid Stimulating Immunoglobulin

Protein

TSI • Concentration / Level • Categorical (e.g., Positive / Negative / Indeterminate)

LOINC Codes

Order Codes

30567-2

Result Codes

30567-2

Result Turnaround Time

2-4 days

Specimen

Serum

Volume

1 mL

Minimum Volume

0.3 mL

Container

Red-top tube, gel-barrier tube, lavender-top (EDTA) tube or green-top (heparin) tube

Collection Instructions

Serum or plasma must be separated from blood cells by centrifugation, ideally within two hours of collection. If red-top tube or plasma, transfer separated serum or plasma to a plastic transport tube.