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HelpTest ID: SSATR Supersaturation Profile, Random, Urine
Reporting Name
Supersaturation, Peds, Random, UUseful 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. This 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
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 also present in 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 those urinary supersaturations that are identified. Treatment strategies include alterations in diet and fluid intake as well as drug therapy, all designed to decrease the urine supersaturation.
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 even more positive in those individuals who do form kidney stones. The reference values are simply 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 suggests 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 for calcium phosphate. Of note, a urine pH of less than 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 greater than 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)
Brushite: 0.21 DG
Hydroxyapatite: 3.96 DG
Uric acid: 1.04 DG
Sodium urate: 1.76 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, et al: Urinary oxalate and urate to creatinine ratios in a healthy pediatric population. Am J Kidney Dis. 1999;34: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, et al: Urinary oxalate and urate to creatinine ratios in a healthy pediatric population. Am J Kidney Dis. 1999;34: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, et al: Urinary phosphate/creatinine, calcium/creatinine, and magnesium/creatinine ratios in a healthy pediatric population. J Pediatr. 1997;131:252-257
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, et al: Urinary phosphate/creatinine, calcium/creatinine, and magnesium/creatinine ratios in a healthy pediatric population. J Pediatr. 1997;131:252-257
Citrate/Creatinine (mg/mg)
|
Age (year) |
95th Percentile |
|
5-18 |
<1.311 |
Srivastava T, Winston MJ, Auron A, et al: Urine calcium/citrate ratio in children with hypercalciuric stones. Pediatr Res. 2009;66:85-90
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| RRSUP | Supersaturation, Random, U | No | Yes |
| NAUR | Sodium, Random, U | Yes, (order RNAUR) | Yes |
| KURR | Potassium, Random, U | Yes, (order RKUR) | Yes |
| CACR2 | Calcium, Random, U | Yes, (order CACR3) | Yes |
| MAGR | Magnesium, Random, U | Yes, (order MAGRU) | Yes |
| CLUR | Chloride, Random, U | Yes, (order RCHLU) | Yes |
| POUR | Phosphorus, Pediatric, Random, U | Yes, (order RPHOC) | Yes |
| SULFR | Sulfate, Random, U | No | Yes |
| CITRR | Citrate Excretion, Peds, Random, U | Yes, (order CITRA) | Yes |
| OXUR | Oxalate, Pediatric, Random, U | Yes, (order ROXUR) | Yes |
| UPHR | pH, Random, U | No | Yes |
| URCUR | Uric Acid, Random, U | Yes, (order RURC1) | Yes |
| CTURR | Creatinine, Random, U | Yes, (order RCTUR) | Yes |
| UOSMR | Osmolality, Random, U | No | Yes |
| RAMCN | Ammonium, Random, U | Yes, (order RAMBO) | Yes |
Report Available
2 to 5 daysDay(s) Performed
Monday through Friday
Clinical Reference
1. Werness PG, Brown CM, Smith LH, Finlayson B: EQUIL2: a BASIC computer program for the calculation of urinary saturation. J Urol. 1985 Dec;134(6):1242-1244
2. Parks JH, Coward M, Coe FL: Correspondence between stone composition and urine supersaturation in nephrolithiasis. Kidney Int. 1997 Mar;51(3):894-900
3. Finlayson B: Calcium stones: Some physical and clinical aspects. In: David DS, ed. Calcium Metabolism in Renal Failure and Nephrolithiasis. John Wiley and Sons; 1977:337-382
4. Burtis CA, Bruns DE: Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics. 7th ed. Saunders; 2014
5. Tiselius HG, Daudon M, Thomas K, Seitz C: Metabolic work-up of patients with urolithiasis: indications and diagnostic algorithm. Eur Urol Focus. 2017 Feb;3(1):62-71. doi: 10.1016/j.euf.2017.03.014
Method Name
CITRR, RAMCN OXUR: Enzymatic
UOSMR: Freezing Point Depression
SULFR: High-Performance Ion Chromatography (HPIC)
MAGR: Colorimetric Endpoint Assay
CACR2: Photometric
POUR: Molybdic Acid
UPHR: pH Meter
NAUR, KURR, CLUR: Potentiometric, Indirect Ion-Selective Electrode (ISE)
CTURR: Enzymatic Colorimetric Assay
URCUR: Uricase
Specimen Type
UrineOrdering Guidance
A timed 24-hour urine collection is the preferred specimen for measuring and interpreting this profile to determine kidney stone risk factors (order SAT24 / Supersaturation Profile, 24 Hour, Urine. Random 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.
Additional Testing Requirements
Necessary Information
Patient's age is required.
Specimen Required
Supplies:
Urine Tubes, 10 mL (T068)
Aliquot Tubes, 5 mL (T465)
Container/Tube: 3 Plastic, 10-mL urine tubes and 4 plastic, 5-mL tubes
Specimen Volume: 40 mL
Collection Instructions:
1. Collect a random urine specimen and divide the urine into 6 tubes.
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 over 8 indicate bacterial contamination and testing will be canceled. Do not attempt to adjust pH as it will adversely affect results.
Specimen Minimum Volume
30 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated | 14 days |
Reference Values
pH: 4.5 to 8.0
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 patient younger than 18 years and older than 77 years of age
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 than1 month of age.
Reference values have not been established for patients who are older than 83 years of age.
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 of age.
Reference values have not been established for patients who are older than 83 years of age
Test Classification
This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test 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 |
|---|---|---|
| SSATR | Supersaturation, Peds, Random, U | In Process |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| SULFR | Sulfate, Random, U | 2975-1 |
| UOSMR | Osmolality, Random, U | 2695-5 |
| UPHR | pH, Random, U | 2756-5 |
| CITR1 | Citrate Concentration, Peds, Random, U | 2128-7 |
| RCHLU | Chloride, Random, U | 2078-4 |
| RCTUR | Creatinine, Random, U | 2161-8 |
| RKUR | Potassium, Random, U | 2828-2 |
| RNAUR | Sodium, Random, U | 2955-3 |
| OXCON | Oxalate, Pediatric, Random, U | 15086-2 |
| 31241 | Calcium Oxalate Crystal | In Process |
| POCON | Phosphorus, Pediatric, Random, U | 2778-9 |
| URCO2 | Uric Acid, Random, U | 3086-6 |
| MGCON | Magnesium, Random, U | 19124-7 |
| CALC4 | Calcium, Random, U | 17862-4 |
| RAMCN | Ammonium, Random, U | 1842-4 |
| CACTR | Calcium/Creatinine Ratio | 9321-1 |
| MGCTR | Magnesium/Creatinine Ratio | 13474-2 |
| RATO6 | Uric Acid/Creat Ratio, Random, U | 3089-0 |
| RATO5 | Phosphorus/Creatinine Ratio | 11141-9 |
| 31242 | Brushite Crystal | In Process |
| OXCO2 | Oxalate Concentration | 2700-3 |
| RATO8 | Citrate/Creatinine Ratio | 13722-4 |
| RATO7 | Oxalate/Creatinine Ratio | 13483-3 |
| 31243 | Hydroxyapatite Crystal | In Process |
| 31244 | Uric Acid Crystal | In Process |
| 31245 | Sodium Urate Crystal | In Process |
| 31246 | Interpretation | 69051-1 |
Forms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.
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