Diagnostic Use
Evaluates thyroid function; helps diagnose hypothyroidism or hyperthyroidism.
Interpretation
Interpretation usually requires concomitant fT4 +/- fT3 level.
Increased in primary hypothyroidism. Other causes include secondary hypothyroidism due to pituitary disorders, autoimmune thyroiditis, poor compliance with thyroxine therapy, amiodarone, lithium, TSH resistance, TSH secreting pituitary adenoma or assay interference.
Decreased in hyperthyroidism. Other causes include Non-thyroidal illness, first trimester pregnancy, drugs (steroids, dopamine), thyroiditis, central hypothyroidism, isolated TSH deficiency or assay interference.
Test Method
Principle: Third-generation assay Fluorescein (FITC) labelled antibodies
Reagents: Siemens Atellica IM TSH3-Ultra II
Analyser: Siemens Atellica IM
Limitations / Interference
Patient samples may contain heterophilic antibodies that could react in immunoassays to give falsely elevated or depressed results.
For patient samples containing fluorescein (undergoing retinal fluorescein angiography), use of Siemens Atellica Solution and CI methods is not recommended as it can decrease results in this assay.