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Test ID RTRP2 Tubular Reabsorption of Phosphorus, Random Urine and Serum


Specimen Required


Both serum and urine are required.

 

Patient Preparation:

Fasting: 12 hours, required

 

Specimen Type: Serum

Supplies: Sarstedt Aliquot Tube, 5 mL (T914

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL Serum

Collection Instructions:

1. Centrifuge and aliquot serum into a plastic vial.

2. Label specimen as serum.

 

Specimen Type: Urine

Container/Tube: Plastic, 5-mL tube

Specimen Volume: 4 mL

Collection Instructions:

1. Collect a random urine specimen.

2. No preservative.

3. Label specimen as urine.


Secondary ID

614047

Useful For

Assessing renal reabsorption of phosphorus in a variety of pathological conditions associated with hypophosphatemia including hypophosphatemic rickets, tumor-induced osteomalacia, and tumoral calcinosis

 

Adjusting phosphate replacement therapy in severe deficiency states monitoring the renal tubular recovery from acquired Fanconi syndrome

Specimen Type

Serum
Urine

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 7 days
  Frozen  90 days
Urine Refrigerated (preferred) 14 days
  Frozen  30 days
  Ambient  7 days

Reject Due To

Gross hemolysis Reject

Reference Values

TUBULAR REABSORPTION OF PHOSPHORUS

>80%

(Although, tubular reabsorption of phosphorus levels must be interpreted in light of the prevailing plasma phosphorus and glomerular filtration rate.)

 

TUBULAR MAXIMUM PHOSPHORUS REABSORPTION/GLOMERULAR FILTRATION RATE (TmP/GFR)

2.6-4.4 mg/dL (0.80-1.35 mmol/L)

 

PHOSPHORUS (INORGANIC)

Males

<1 year: Not established

1-4 years: 4.3-5.4 mg/dL

5-13 years: 3.7-5.4 mg/dL

14-15 years: 3.5-5.3 mg/dL

16-17 years: 3.1-4.7 mg/dL

≥18 years: 2.5-4.5 mg/dL

 

Females

<1 year: Not established

1-7 years: 4.3-5.4 mg/dL

8-13 years: 4.0-5.2 mg/dL

14-15 years: 3.5-4.9 mg/dL

16-17 years: 3.1-4.7 mg/dL

≥18 years: 2.5-4.5 mg/dL

 

PHOSPHORUS, RANDOM URINE

No established reference values

 

Random urine phosphorus may be interpreted in conjunction with serum phosphorus, using both values to calculate fractional excretion of phosphorus.

 

The calculation for fractional excretion (FE) of phosphorus (P) is

FE(P)= ([P(urine)XCreat(serum)]/[P(serum)XCreat(urine)]) X 100

 

CREATININE, SERUM

Males*

0-11 months: 0.17-0.42 mg/dL

1-5 years: 0.19-0.49 mg/dL

6-10 years: 0.26-0.61 mg/dL

11-14 years: 0.35-0.86 mg/dL

≥15 years: 0.74-1.35 mg/dL

 

Females*

0-11 months: 0.17-0.42 mg/dL

1-5 years: 0.19-0.49 mg/dL

6-10 years: 0.26-0.61 mg/dL

11-15 years: 0.35-0.86 mg/dL

> or=16 years: 0.59-1.04 mg/dL 

 

*Kulasingam V, Jung BP, Blaustig IM, et al. Pediatric reference intervals for 28 chemistries and immunoassays on the Roche cobas 6000 analyzer--a CALIPER pilot study. Clin Biochem. 2010;43(13-14):1045-1050

 

CREATINE, RANDOM URINE

<18 years: Not established

≥18 years: 16-326 mg/dL

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

82565

82570

84100

84105

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 day