Test Entry - Detail

Renal Phosphate Threshold (TmPi)

General

Clinical Use:

This test is used to assess the renal tubular reabsorption of phosphate and to identify and differentiate between disorders of phosphate metabolism.
It can help to identify phosphaturia in patients with hypophosphataemia. A low TmPi suggests renal phosphate wasting, which may be seen with high activity of PTH or FGF-23 and in renal tubular disorders.
Increased TmPi may be seen with growth hormone excess, hypoparathyroidism or pseudohypoparathyroidism.
A paired blood and spot urine collection is required, preferably in the early morning and fasting state.

Availability:

Samples are tested routinely during the testing laboratory's hours of operation.

Aliases/Synonyms:

TmP/GFR, Tubular Maximum Reabsorption of Phosphate,

Code:

TMPI

Handling Instructions (to laboratory):

Send sample chilled.

Hyperlink:

Reference Interval:

0d to <16y:   1.15 - 2.44 mmol/L GF
16y to <20y:  0.95 - 1.75 mmol/L GF
20y to 120y:  0.75 - 1.35 mmol/L GF

Collection Requirements

Container:

Lithium Heparin-PST (GREEN), and, Urine Container (URINE),

Sample Type:

See container

Minimum Collection Volume:

Collection Instructions:

Samples are required to be collected in the early morning and patient must be fasting.
Blood and spot urine samples must be collected at the same time.

Processing Requirements

Alternate Containers:

Serum Sep. Tube-SST (GOLD)

and

Urine Container (URINE)

Processing Instructions:

Minimum Assay Volume:

Stability:

Transport Instructions (to testing laboratory):

Send sample chilled.

Testing Locations

Performed at:

Section	Department	Site	Contact Phone
Core	Biochemistry	Fiona Stanley Hospital	6152 8140
Core	Biochemistry	Fremantle Hospital	9431 2382
Core	Biochemistry	QEII Medical Centre	6383 4093
Core	Biochemistry	Royal Perth Hospital	9224 1176

Last Updated : 15-08-2025 13:19