Free Thyroxine Index

Diagnostic Use

FTI (free thyroxine index) is calculated by measuring Thyroid Uptake (TU) and multiplying by TT4.

FTI = (T4 x TU)/TU median of Reference interval.

Useful when there are changes in thyroxine-binding globulin (TBG).

Test requests require pre-approval by a chemical pathologist.

Department

Endocrinology Lab

Delphic Registration Code

FTI

Synonyms

Free T4 index
FTI

Turnaround Time

3 days

Specimen Type

• Serum
• Plasma

Specimen Requirements

Tube/Container Type:

Preferred

• Serum (Red Cap)

Preferred if West Coast

• SST II (Gold Cap)

Acceptable

• SST II (Gold Cap)
• Lithium Heparin - Non-gel (Green Cap)
• Lithium Heparin - Gel (Light Green Cap)

Preferred Sample Volume (ml)

5

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• Serum (Red Cap)

Acceptable

• SST II (Gold Cap)
• Lithium Heparin - Non-gel (Green Cap)
• Lithium Heparin - Gel (Light Green Cap)

Preferred Sample Volume (ml)

1.0

Aliquot Instructions

Sample Type

• Serum
• Plasma

Minimum Volume (ml)

1.0

Transport to Lab

Frozen
If overnight - Frozen

Additional Referral/Aliquot Information

Minimum 1.0 ml serum. Ideally 1.5ml serum. This volume allows all total thyroid function tests to be performed.

Reference Intervals

75-170 nmol/L (manufacturer’s data).

Test Method

Beckman-Coulter Access Analyser - CMIA

Non-Funded Test Cost

$32.09 (Exclusive of GST)

Billing Code

8867

EDTA not acceptable.

Contact Information

Enquiry Form