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HelpTest Code ORTHP Orthostatic Proteinuria, Random, Urine
Specimen Required
Patient Preparation: Specimens should be collected before fluorescein is given or not collected until at least 24 hour later.
Container/Tube: Plastic, 5-mL tube
Specimen Volume: 4 mL
Collection Instructions:
1. This is a nighttime (supine) collection.
2. Void immediately prior to lying down to sleep.
3. Collect an 8-hour (nighttime) urine specimen.
4. Upon awaking in the morning, the patient should immediately void into the specimen cup.
4. No preservative.
5. Invert well before taking 4-mL (maximum) aliquot.
Secondary ID
617766Useful For
Diagnosis of orthostatic proteinuria
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| PRCON | Protein, Total, Random, U | No | Yes |
| RATO2 | Protein/Creatinine Ratio | No | Yes |
| CRETR | Creatinine, Random, U | No | Yes |
Method Name
PRCON: Turbidimetry
CRETR: Enzymatic Colorimetric Assay
RATO2: Calculation
Reporting Name
Orthostatic Proteinuria, Random, USpecimen Type
UrineSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 14 days | |
| Frozen | 30 days | ||
| Ambient | 24 hours |
Reject Due To
| All specimens will be evaluated at Mayo Clinic Laboratories for test suitability. |
Clinical Information
Orthostatic proteinuria refers to the development of increased proteinuria that develops only when the person is upright and resolves when recumbent or supine. This condition is usually seen in children, adolescents, or young adults, and accounts for the majority of cases of proteinuria in childhood.
Orthostatic proteinuria usually does not indicate significant underlying renal pathology, and is usually not associated with other urine abnormalities such as hypoalbuminemia, hematuria, red blood cell casts, fatty casts, etc. Orthostatic proteinuria typically resolves over time.
This test evaluates for this condition by demonstrating either significant proteinuria, even while supine, or normal protein excretion. Significant proteinuria, even while supine, suggests that the patient does not have orthostatic proteinuria while normal protein excretion supports the diagnosis. This test is typically done on three consecutive mornings to provide more robust support for the diagnosis.
Reference Values
PROTEIN/CREATININE RATIO:
≥18 years: <0.18 mg/mg creatinine
CREATININE:≥18 years = 16-326 mg/dL
Reference values have not been established for patients younger than 18 years of age.
Interpretation
First-morning urine protein-to-creatinine ratio below 0.20 mg/mg creatinine supports the diagnosis of orthostatic proteinuria, while a result above 0.20 mg/mg creatinine does not support this diagnosis.
Further investigation into other etiologies for proteinuria may be warranted.
Method Description
Protein:
The sample is preincubated in an alkaline solution containing EDTA, which denatures the protein and eliminates interference from magnesium ions. Benzethonium chloride is then added, producing turbidity.(Package insert: Total Protein Urine/CSF. Roche Diagnostics; V13.0, 11/2018)
Creatinine:
The enzymatic method is based on the determination of sarcosine from creatinine with the aid of creatininase, creatinase, and sarcosine oxidase. The liberated hydrogen peroxide is measured via a modified Trinder reaction using a colorimetric indicator. Optimization of the buffer system and the colorimetric indicator enables the creatinine concentration to be quantified both precisely and specifically.(Package insert: Creatinine plus v2. Roche Diagnostics; V15.0, 03/2019)
The final result uses a calculation to provide the total protein per creatinine ratio. This calculation is performed by the laboratory information system, SCC Soft.
Day(s) Performed
Monday through Sunday
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
CRETR- 82570
PRCON- 84156
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| ORTHP | Orthostatic Proteinuria, Random, U | 87434-7 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| CRETR | Creatinine, Random, U | 2161-8 |
| PRCON | Protein, Total, Random, U | 2888-6 |
| RATO2 | Protein/Creatinine Ratio | 2890-2 |