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Test Code B0004
Test Summary

This biochemical test analyzes the level of thyroxine (T4)

Turn-Around-Time (TAT)* 3  days
Acceptable Sample Types
Dried Blood Spots
Acceptable Billing Types
Self (patient) Payment
Institutional Billing
*TAT starts after the sample and all required sample information is received at PerkinElmer Genomics, or after the benefits investigation is complete if requested for commercial insurance billing.

Low levels of thyroxine are associated with congenital hypothyroidism.

  • Infants with symptoms of hypothyroidism, sleepiness, decreased activity, difficulty feeding, constipation, intellectual disability, and growth retardation.
  • Individuals with a family history of congenital hypothyroidism.

Congenital hypothyroidism is a disease associated with loss of function of the thyroid gland. Onset is in infancy, and symptoms can include sleepiness, decreased activity, difficulty feeding, constipation, intellectual disability, and growth retardation. The incidence of congenital hypothyroidism is estimated to be ~ 1 in 2,000.

Fluoroimmunometric assay is based on the direct sandwich technique in which two antibodies are directed against a given analyte. Calibrators and serum samples containing the analyte are reacted with immobilized monoclonal antibodies directed against the analyte. Europium-labeled monoclonal antibodies directed against an antigenic site on the analyte are reacted with the analyte bound to the solid-phase antibody.  The Inducer dissociates europium ions from the labeled antibodies into the solution, where they form highly fluorescent chelates with components of the Inducer. The fluorescence in each cup is then measured. The europium fluorescence from each sample is proportional to the analyte concentration in the sample.

Dried Blood Spots
Collection Container(s):

Dried blood spot card


Follow kit instructions. Briefly, allow blood to saturate card until indicated areas are filled and blood has soaked through card. Air dry card at ambient temperature for at least 3 hours.

  • NBS: Please contact PKIG to request the StepOne® kit.
  • Gene Sequencing: Please contact PKIG to request the DBS collection kit.
  • For pre-punched DBS: The required minimum 6 punches with 3.2 mm or 4 punches 4.75 mm.
Condition: Follow the instructions provided with the collection set. Store the dried blood at ambient temperature for up to two days. If the specimen cannot be sent as soon as it is dry, the filter paper should be placed in a sealable plastic bag and stored in a refrigerator (≤ 8°C) or preferably in a freezer.
Shipping: Follow kit instructions. Double bag and ship overnight at ambient temperature.

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