Test Code 4017044 Thyroid Cascade

Important Note

When this test is ordered a TSH will be run first.

If the TSH is normal, no other testing will be performed.

If the TSH is abnormal (≤0.35 or ≥5.5) it will reflex to a Free T4.

If the Free T4 is normal (<1.9) and the TSH is <0.1 it will reflex to a Total T3 (performed by UVMC).

1.5mL serum or heparinized plasma
NOTE: Serum/plasma should be separated from cells within 2 hours of collection.

SST (tiger, gold, or red top) tube prefered

Lithium Heparan PST (light green top) tube is acceptable.

750µL serum/plasma

24 hours at room temperature, 7 days at 2-8°C
May be frozen at -20°C for 1 month

TSH & FT4: Same Day

Total T3: 2-3 days

7 Days

TSH & FT4: Chemiluminescent Immunoassay

Total T3: Competitive Immunoassay

84443

Springfield Hospital Laboratory

Improperly labeled sample

Sample stabilized with sodium azide