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HelpTest Code RPTU1 Protein/Creatinine Ratio, Random, Urine
Specimen Required
Patient Preparation: Specimens should be collected before fluorescein is given or not collected until at least 24 hour later.
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Container/Tube: Plastic vial
Specimen Volume: 4 mL
Collection Instructions:
1. Collect a random urine specimen.
2. No preservative.
3. Invert well before taking 4 mL aliquot.
4. Do not over fill aliquot tube, 4 mL at most.
Secondary ID
614004Useful For
Evaluation of renal disease
Screening for monoclonal gammopathy
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| PTCON | Protein, Total, Random, U | No | Yes |
| RATO3 | Protein/Creatinine Ratio | No | Yes |
| CRETR | Creatinine, Random, U | No | Yes |
Method Name
PTCON: Turbidimetry
CRETR: Enzymatic Colorimetric Assay
RATO3: Calculation
Reporting Name
Protein/Creatinine Ratio, 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
Protein in urine is normally composed of a combination of plasma-derived proteins that have been filtered by glomeruli and have not been reabsorbed by the proximal tubules and proteins secreted by renal tubules or other accessory glands.
Increased amounts of protein in the urine may be due to:
-Glomerular proteinuria: Caused by defects in permselectivity of the glomerular filtration barrier to plasma proteins (eg, glomerulonephritis or nephrotic syndrome)
-Tubular proteinuria: Caused by incomplete tubular reabsorption of proteins (eg, interstitial nephritis)
-Overflow proteinuria: Caused by increased plasma concentration of proteins (eg, multiple myeloma, myoglobinuria)
Reference Values
≥18 years: <0.18 mg/mg creatinine
Reference values have not been established for patients younger than 18 years of age.
Interpretation
Total protein of greater than 500 mg/24 hours should be evaluated by immunofixation to determine if a monoclonal immunoglobulin light chain is present and, if so, identify it as either kappa or lambda type.
Urinary protein levels may rise to 300 mg/24 hours in healthy individuals after vigorous exercise.
Low-grade proteinuria may be seen in inflammatory or neoplastic processes involving the urinary tract.
In a random urine specimen, a protein:creatinine or protein:osmolality ratio can be used to roughly approximate 24-hour excretion rates. The normal protein-to-osmolality ratio is less than 0.42.(1) For patients younger than 18 years of age, no reference range has been established.
Cautions
False proteinuria may be due to contamination of urine with menstrual blood, prostatic secretions, or semen.
Normal newborn infants may have higher excretion of protein in urine during the first 3 days of life.
The presence of hemoglobin elevates protein concentration.
Protein electrophoresis and immunofixation may be required to characterize and interpret the proteinuria.
Clinical Reference
1. Brunzel N: Chemical examination of urine. In: Fundamentals of Urine and Body Fluids. 4th ed. Saunders; 2018:92-94
2. Wilson DM, Anderson RL: Protein-osmolality ratio for the quantitative assessment of proteinuria from a random urinalysis sample. Am J Clin Pathol. 1993 Oct;100(4):419-424
3. Morgenstern BZ, Butani L, Wollan P, Wilson DM, Larson TS: Validity of protein-osmolality versus protein-creatinine ratios in the estimation of quantitative proteinuria from random samples of urine in children. Am J Kidney Dis. 2003 Apr;41(4):760-766
4. Rinehart BK, Terrone DA, Larmon JE, Perry KG Jr, Martin RW, Martin JN Jr: A 12-hour urine collection accurately assesses proteinuria in hospitalized hypertensive gravida. J Perinatol. 1999 Dec;19(8 Pt 1):556-558
5. Adelberg AM, Miller J, Doerzbacher M, Lambers DS: Correlation of quantitative protein measurements in 8-, 12-, and 24-hour urine samples for diagnosis of preeclampsia. Am J Obstet Gynecol. 2001 Oct;185(4):804-807
6. Robinson RR: Isolated proteinuria in asymptomatic patients. Kidney Int. 1980 Sep;18(3):395-406
7. Dube J, Girouard J, Leclerc P, Douville P: Problems with the estimation of urine protein by automated assays. Clin Biochem. 2005 May;(38):479-485
8. Koumantakis G, Wyndham L: Fluorescein interference with urinary creatinine and protein measurements. Clin Chem. 1991 Oct;37(10 Pt 1):1799
9. Lamb EJ, Jones GRD: Kidney function tests. In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:479-517
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)
Specimen Retention Time
7 daysPerforming 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
84156
82570
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| RPTU1 | Protein/Creatinine Ratio, Random, U | 87434-7 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| PTCON | Protein, Total, Random, U | 2888-6 |
| CRETR | Creatinine, Random, U | 2161-8 |
| RATO3 | Protein/Creatinine Ratio | 2890-2 |
Day(s) Performed
Monday through Sunday
Report Available
Same day/1 dayForms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.