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Test Code SUPRA Supersaturation Profile, Random, Urine


Ordering Guidance


A timed 24-hour urine collection is the preferred specimen for measuring and interpreting this profile to determine kidney stone risk factors (SUP24 / Supersaturation Profile, 24 Hour, Urine). Random urine collections with individual analytes normalized to urinary creatinine may be of some clinical use in patients who cannot collect a 24-hour specimen, typically small children. Therefore, this test is offered on random collections for children less than 16 years old.

 

X-ray dyes and contrast media will affect uric acid test results.

-If a kidney X-ray with dye or computerized tomography (CT) scan with contrast has been performed, patient should wait a minimum of 1 day before starting collection.

-If a cholangiography (bile duct X-ray) has performed, patient should wait 7 days before starting collection.

-Urine must be collected before tablets have been taken for gallbladder X-ray, otherwise patient should wait 7 days before starting collection.



Necessary Information


Patient's age is required.



Specimen Required


Supplies:

-Urine Tubes, 10 mL (T068)

-Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube: 90 mL urine container

Submission Container/Tube: 2 x 10 mL plastic urine tubes and 5 x 5 mL plastic urine tubes

Specimen Volume: 40 mL

Collection Instructions:

1. Collect a random urine specimen, mix collection container thoroughly and divide the urine into 7 plastic tubes (2 x 10 mL and 5 x 5 mL).

2. Refrigerate specimen after collection. Specimen pH should be between 4.5 and 8 and will stay in this range if kept refrigerated. Specimens with pH above 8 indicate bacterial contamination, and testing will be canceled. Do not attempt to adjust pH as it will adversely affect results.


Useful For

Diagnosis and management of patients with renal lithiasis:

-Predicting the likely composition of the stone, in patients who have a radiopaque stone, for whom stone analysis is not available which may help in designing a treatment program

-Identifying specific risk factors for stones formation using a random urine collection

-Monitoring the effectiveness of therapy by confirming that the crystallization potential has indeed decreased

-Evaluation of kidney excretion of acid and urine pH

Profile Information

Test ID Reporting Name Available Separately Always Performed
SRINT Supersaturation, Random, U 1 No Yes
RANAU Sodium, Random, U Yes, (order RNAUR) Yes
RAKUR Potassium, Random, U Yes, (order RKUR) Yes
RACAL Calcium, Random, U Yes, (order CACR3) Yes
RAMAG Magnesium, Random, U Yes, (order MAGRU) Yes
RACLU Chloride, Random, U Yes, (order RCHLU) Yes
RAPOU Phosphorus, Random, U Yes, (order RPHOC) Yes
RASUL Sulfate, Random, U No Yes
RACIT Citrate Excretion, Random, U Yes, (order CITRA) Yes
RAOXU Oxalate, Random, U Yes, (order ROXUR) Yes
RAPHU pH, Random, U No Yes
RAURA Uric Acid, Random, U Yes, (order RURC1) Yes
RACTU Creatinine, Random, U Yes, (order RCTUR) Yes
RAOSM Osmolality, Random, U No Yes
RAAMM Ammonium, Random, U Yes, (order RAMBO) Yes

Method Name

RACIT, RAAMM, RAOXU: Enzymatic

RAOSM: Freezing Point Depression

RASUL: High-Performance Ion Chromatography (HPIC)

RAMAG: Colorimetric Endpoint Assay

RACAL, RAPOU: Photometric

RAPHU: pH Meter

RANAU, RAKUR, RACLU: Potentiometric, Indirect Ion-Selective Electrode (ISE)

RACTU: Enzymatic Colorimetric Assay

RAURA: Uricase

Reporting Name

Supersaturation, Random, U

Specimen Type

Urine

Specimen Minimum Volume

30 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 14 days
  Frozen  14 days
  Ambient  72 hours

Reject Due To

pH <4.5 or >8.0 Reject

Clinical Information

Urine is often supersaturated, which favors precipitation of several crystalline phases such as calcium oxalate, calcium phosphate, and uric acid. However, crystals do not always form in supersaturated urine because supersaturation is balanced by crystallization inhibitors that are present in the urine. Urinary inhibitors include ions (eg, citrate) and macromolecules but remain poorly understood.

 

Urine supersaturation is calculated by measuring the concentration of all the ions that can interact (potassium, calcium, phosphorus, oxalate, uric acid, citrate, magnesium, sodium, chloride, sulfate, and pH). Once the concentrations of all the relevant urinary ions are known, a computer program can calculate the theoretical supersaturation with respect to the important crystalline phases (eg, calcium oxalate).(1)

 

Since the supersaturation of urine has been shown to correlate with stone type,(2) therapy is often targeted towards decreasing the urinary supersaturations identified. Treatment strategies include alterations in diet and fluid intake as well as drug therapy; all designed to decrease the urine supersaturation.

Reference Values

The following analytes do not have any established reference values:

Sodium, potassium, chloride, phosphorus, citrate, sulfate, and oxalate

pH: 4.5-8.0

 

CREATININE

≥18 years old: 16-326 mg/dL

Reference values have not been established for patients who are younger than 18 years.

 

OSMOLALITY

0-11 months: 50-750 mOsm/kg

≥12 months: 150-1,150 mOsm/kg

 

AMMONIUM

18-77 years: 3-65 mmol/L

No reference values established for patients who are younger than 18 years or older than 77 years.

 

CALCIUM

1 month-<12 months: 0.03-0.81 mg/mg creat

12 months-<24 months: 0.03-0.56 mg/mg creat

24 months-<3 years: 0.02-0.50 mg/mg creat

3 years-<5 years: 0.02-0.41 mg/mg creat

5 years-<7 years: 0.01-0.30 mg/mg creat

7 years-<10 years: 0.01-0.25 mg/mg creat

10 years-<18 years: 0.01-0.24 mg/mg creat

18 years-83 years: 0.05-0.27 mg/mg creat

Reference values have not been established for patients who are younger than 1 month or older than 83 years.

 

MAGNESIUM

Magnesium/Creatinine Ratio:

1 month-<12 months: 0.10-0.48 mg/mg creat

12 months-<24 months: 0.09-0.37 mg/mg creat

24 months-<3 years: 0.07-0.34 mg/mg creat

3 years-<5 years: 0.07-0.29 mg/mg creat

5 years-<7 years: 0.06-0.21 mg/mg creat

7 years-<10 years: 0.05-0.18 mg/mg creat

10 years-<14 years: 0.05-0.15 mg/mg creat

14 years-<18 years: 0.05-0.13 mg/mg creat

18 years-83 years: 0.04-0.12 mg/mg creat

Reference values have not been established for patients who are younger than 1 month or older than 83 years.

Interpretation

Delta G (DG), the Gibbs free energy of transfer from a supersaturated to a saturated solution, is negative for undersaturated solutions and positive for supersaturated solutions. In most cases, the supersaturation levels are slightly positive, even in normal individuals, but are balanced by an inhibitor activity.

 

While the DG of urine is often positive, even in the urine of non-stone formers, on average, the DG is more positive in those individuals who do form kidney stones. The reference values are derived by comparing urinary DG values for the important stone-forming crystalline phases between a population of stone formers and a population of non-stone formers. Those DG values that are outside the expected range in a population of non-stone formers are marked abnormal.

 

A normal or increased citrate value suggests that potassium citrate may be a less effective choice for treatment of a patient with calcium oxalate or calcium phosphate stones.

 

If the urine citrate is low, secondary causes should be excluded including hypokalemia, renal tubular acidosis, gastrointestinal bicarbonate losses (eg, diarrhea or malabsorption), or an exogenous acid load (eg, excessive consumption of meat protein).

 

An increased urinary oxalate value may prompt a search for genetic abnormalities of oxalate production (ie, primary hyperoxaluria). Secondary hyperoxaluria can result from diverse gastrointestinal disorders that result in malabsorption. Milder hyperoxaluria could result from excess dietary oxalate consumption or reduced calcium (dairy) intake, perhaps even in the absence of gastrointestinal disease.

 

Low urine ammonium and high urine pH suggest renal tubular acidosis. Such patients are at risk of calcium phosphate stones.

 

The results can be used to determine the likely effect of a therapeutic intervention on stone-forming risk. For example, taking oral potassium citrate will raise the urinary citrate excretion, which should reduce calcium phosphate supersaturation (by reducing free ionic calcium), but citrate administration also increases urinary pH (because it represents an alkali load), which promotes calcium phosphate crystallization. The net result of this or any therapeutic manipulation could be assessed by collecting a 24-hour urine and comparing the supersaturation calculation for calcium phosphate before and after therapy.

 

Important stone-specific factors:

-Calcium oxalate stones: Urine volume, calcium, oxalate, citrate, and uric acid excretion are all risk factors that are possible targets for therapeutic intervention.

-Calcium phosphate stones (apatite or brushite): Urinary volume, calcium, pH, and citrate significantly influence the supersaturation of calcium phosphate. Of note, a urine pH below 6 may help reduce the tendency for these stones to form.

-Uric acid stones: Urine pH, volume, and uric acid excretion levels influence the supersaturation. Urine pH is especially critical, in that uric acid is unlikely to crystallize if the pH is above 6.

-Sodium urate stones: Alkaline pH and high uric acid excretion promote stone formation.

 

A low urine volume is a universal risk factor for all types of kidney stones.

 

The following reference means for calculated supersaturation apply to 24-hour timed collections. No information is available for random collections.

Supersaturation Reference Means (Delta G: DG)

Men:

Calcium oxalate: 1.89 DG

Brushite: 0.46 DG

Hydroxyapatite: 4.19 DG

Uric acid: 1.18 DG

 

Women:

Calcium oxalate: 1.59 DG

Brushite: -0.11 DG

Hydroxyapatite: 3.62 DG

Uric acid: 0.89 DG

 

Values for individual analytes that are part of this panel on a random urine collection are best interpreted as a ratio to the creatinine excretion. Following are pediatric reference ranges for the important analytes for which pediatric data is available.

 

Oxalate/Creatinine (mg/mg)

Age (year)

95th Percentile

0-0.5

<0.175

0.5-1

<0.139

1-2

<0.103

2-3

<0.08

3-5

<0.064

5-7

<0.056

7-17

<0.048

 

Matos V, Van Melle G, Werner D, Bardy D, Guignard JP. Urinary oxalate and urate to creatinine ratios in a healthy pediatric population. Am J Kidney Dis. 1999;34(2):e1

 

Uric Acid/Creatinine (mg/mg)

Age (year)

5th Percentile

95th Percentile

0-0.5

>1.189

<2.378

0.5-1

>1.040

<2.229

1-2

>0.743

<2.080

2-3

>0.698

<1.932

3-5

>0.594

<1.635

5-7

>0.446

<1.189

7-10

>0.386

<0.832

10-14

>0.297

<0.654

14-17

>0.297

<0.594

 

Matos V, Van Melle G, Werner D, Bardy D, Guignard JP. Urinary oxalate and urate to creatinine ratios in a healthy pediatric population. Am J Kidney Dis. 1999;34(2):e1

 

Phosphate/Creatinine (mg/mg)

Age (year)

5th Percentile

95th Percentile

0-1

>0.34

<5.24

1-2

>0.34

<3.95

2-3

>0.34

<3.13

3-5

>0.33

<2.17

5-7

>0.33

<1.19

7-10

>0.32

<0.97

10-14

>0.22

<0.86

14-17

>0.21

<0.75

 

Matos V, van Melle G, Boulat O, Markert M, Bachmann C, Guignard JP. Urinary phosphate/creatinine, calcium/creatinine, and magnesium/creatinine ratios in a healthy pediatric population. J Pediatr. 1997;131(2):252-257

 

Magnesium/Creatinine (mg/g)

Age (year)

95th Percentile

0-1

<0.48

1-2

<0.37

2-3

<0.34

3-5

<0.29

5-7

<0.21

7-10

<0.18

10-14

<0.15

14-17

<0.13

 

Matos V, van Melle G, Boulat O, Markert M, Bachmann C, Guignard JP. Urinary phosphate/creatinine, calcium/creatinine, and magnesium/creatinine ratios in a healthy pediatric population. J Pediatr. 1997;131(2):252-257

 

Citrate/Creatinine (mg/mg)

Age (year)

95th Percentile

5-18

<1.311

 

Srivastava T, Winston MJ, Auron A, Alon US. Urine calcium/citrate ratio in children with hypercalciuric stones. Pediatr Res. 2009;66(1):85-90

Day(s) Performed

Monday through Sunday

Report Available

2 to 5 days

Specimen Retention Time

7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

82310-Calcium

82436-Chloride

82507-Citrate excretion

82570-Creatinine

83735-Magnesium

83935-Osmolality

83945-Oxalate

83986-pH

84105-Phosphorus

84133-Potassium

84300-Sodium

84392-Sulfate

84560-Uric acid

82140-Ammonium

LOINC Code Information

Test ID Test Order Name Order LOINC Value
SUPRA Supersaturation, Random, U 101929-8

 

Result ID Test Result Name Result LOINC Value
RASUC Sulfate, Random, U 2975-1
RAPHU pH, Random, U 2756-5
RAOSU Osmolality, Random, U 2695-5
RANAC Sodium, Random, U 2955-3
RACTU Creatinine, Random, U 2161-8
RAKUC Potassium, Random, U 2828-2
RACLC Chloride, Random, U 2078-4
RAAMM Ammonium, Random, U 1842-4
RACAC Calcium, Random, U 17862-4
CITCO Citrate Excretion, Random, U 2128-7
RAMGC Magnesium, Random, U 19124-7
POUCO Phosphorus, Random, U 2778-9
RAUAC Uric Acid, Random, U 3086-6
OXMCO Oxalate, Random, U (mmol/L) 15086-2
616399 Calcium Oxalate Crystal In Process
616400 Brushite Crystal In Process
OXGCO Oxalate, Random, U (mg/L) 2700-3
UACCR Uric Acid/Creat Ratio, Random, U 3089-0
PHOCR Phosphorus/Creat Ratio, Random, U 11141-9
MAGCR Magnesium/Creat Ratio, Random, U 13474-2
CITCR Citrate/Creatinine Ratio, Random, U 13722-4
CALCR Calcium/Creatinine Ratio, Random, U 9321-1
OXUCR Oxalate/Creatinine Ratio, Random, U 13483-3
616401 Hydroxyapatite Crystal In Process
616402 Uric Acid Crystal In Process
31246 Interpretation 69051-1