Test Directory

Thyroid-Stimulating Immunoglobulin, Serum

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Updated Test Information:

Test Description
Thyroid-Stimulating Immunoglobulin, Serum
Synonym(s)
Thyroid-Stimulating Immunoglob
Test ID
TSI
General Information
Useful for:
Second-order testing for autoimmune thyroid disease, including:
-Differential diagnosis of etiology of thyrotoxicosis in patients with ambiguous clinical signs or contraindicated (eg, pregnant or breast-feeding) or indeterminate thyroid radioisotope scans
-Diagnosis of clinically suspected Graves disease (eg, extrathyroidal manifestations of Graves disease: endocrine exophthalmos, pretibial myxedema, thyroid acropachy) but normal thyroid function tests
-Determining the risk of neonatal thyrotoxicosis in a fetus of a pregnant female with active or past Graves disease
-Differential diagnosis of gestational thyrotoxicosis versus first-trimester manifestation or recurrence of Graves disease
-Assessing the risk of Graves disease relapse after antithyroid drug treatment
A combination of TSI / Thyroid-Stimulating Immunoglobulin (TSI), Serum and THYRO / Thyrotropin Receptor Antibody, Serum is useful as an adjunct in the diagnosis of unusual cases of hypothyroidism (eg, Hashitoxicosis).
Specimen Type
Serum
Specimen Requirements
SST
Stability
Frozen (preferred) 60 days
Refrigerated 7 days
Ambient 24 hours
Unacceptable Specimen Conditions
Gross hemolysis Reject
Gross lipemia OK
Gross icterus OK
Methodology
Recombinant Bioassay
Estimated TAT
2-6 days
Testing Schedule
Monday-Friday
CPT Code(s)
84445
Minimum Sample Volume
0.1 mL
Reference Range
< or =1.3 TSI index
Reference values apply to all ages.
Performing Lab
Mayo
LOINC Code(s)
30567-2