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Mayo Clinic Laboratories

Test Code OPTU Orthostatic Protein, Timed Collection, Urine

Reporting Name

Orthostatic Protein, U

Useful For

Diagnosis of orthostatic proteinuria

As a second-order test for additional characterization of proteinuria of less than 3 grams/24 hours, particularly in children or adolescents

Profile Information

Test ID	Reporting Name	Available Separately	Always Performed
DOPTU	Daytime Orthostatic Protein, U	No	Yes
NOPTU	Nighttime Orthostatic Protein, U	No	Yes

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Urine

Ordering Guidance

This collection process requires 2 separate urine collections within a 24-hour period.

Collect specimen per instructions in Orthostatic Protein Measurement 24-Hour Urine: Collection Site Instructions (T546) in Special Instructions.

Necessary Information

This collection process requires 2 separate urine collections within a 24-hour period.

-Submit start and end times for collection and 16-hour volume (required).

-Submit start and end times for collection and 8-hour volume (required).

Specimen Required

Specimens should be collected before fluorescein is given or not collected until at least 24 hour later.

Supplies: 2 Sarstedt 5 mL Aliquot Tube (T914)

Daytime Collection

Container/Tube: Plastic, 5-mL tube

Specimen Volume: 4 mL

Collection Instructions:

1. Collect a 16-hour (daytime) urine specimen.

2. No preservative.

3. Invert well before taking 4-mL aliquot.

4. Do not over fill aliquot tube 4 mL at most.

5. Collect specimen per instructions in Orthostatic Protein Measurement 24-Hour Urine: Collection Site Instructions (T546) in Special Instructions.

Nighttime (Supine) Collection

Container/Tube: Plastic, 5-mL tube

Specimen Volume: 4 mL

Collection Instructions:

1. Collect an 8-hour (nighttime) urine specimen.

2. No preservative.

3. Invert well before taking 4-mL aliquot at most.

Specimen Minimum Volume

1 mL from 16-hour (daytime) urine collection/1 mL from 8-hour (nighttime) urine collection

Specimen Stability Information

Specimen Type	Temperature	Time
Urine	Refrigerated (preferred)	14 days
	Frozen	30 days
	Ambient	24 hours

Special Instructions

Reference Values

Nighttime (supine) collection: <68 mg/8 hours

Reference values have not been established for patients <18 years of age.

Daytime collection: <197 mg/16 hours

Reference values have not been established for patients <18 years of age

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 x 2

LOINC Code Information

Test ID	Test Order Name	Order LOINC Value
OPTU	Orthostatic Protein, U	1755-8

Result ID	Test Result Name	Result LOINC Value
DPTU	Total Protein, 16 HR, U	49002-9
NPTU	Total Protein, 8 HR, U	50209-6
DUR7	Nighttime collection duration	13362-9
DUR4	Daytime collection duration	13362-9
DVOL	Day volume	19153-6
VL	Night volume	19153-6
NPRO	Total Protein Conc, 8 HR, U	35663-4
DPRO	Total Protein Conc, 16 HR, U	35663-4

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 characterizes this condition by obtaining 2 urine collections within a 24-hour time frame, one collection obtained while the person is recumbent or supine, the other when upright.

Interpretation

A supine 8-hour urine protein excretion of less than 68 mg/8 hours together with either 1) an elevated upright (16-hour) excretion of greater than 197 mg/16 hours, or 2) a 24-hour urine protein excretion of greater than 228 mg/24 hours is considered consistent with orthostatic proteinuria.

Cautions

It is not unusual for urine protein excretion derived from supine collections to be somewhat lower than protein excretion derived from upright collections. However, orthostatic or postural proteinuria is characterized by a supine excretion rate of less than 50 mg/8 hours.

False-proteinuria may be due to contamination of urine with menstrual blood, prostatic secretions, or semen.

The urinary protein concentration may rise to 300 mg/24 hours in healthy individuals after vigorous exercise.

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. Rinehart BK, Terrone DA, Larmon JE, et al: A 12-hour urine collection accurately assesses proteinuria in hospitalized hypertensive gravida. J Perinatol. 1999;19:556-558

2. 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

3. Rytand DA, Spreiter S: Prognosis in postural (orthostatic) proteinuria: forty to fifty-year follow-up of six patients after diagnosis by Thomas Addis. N Engl J Med. 1981;305(11):618-621

4. Robinson RR: Isolated proteinuria in asymptomatic patients. Kidney Int. 1980;18:395-406

5. Dube J, Girouard J, Leclerc P et al: Problems with the estimation of urine protein by automated assays. Clin Biochem. 2005:38(5) 479-485

6. Koumantakis G, Wyndham, L: Fluorescein interference with urinary creatinine and protein measurements. Clin Chem. 1991;37(10):1799

7. 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

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)

Specimen Retention Time

7 days

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Method Name

Turbidimetry

Forms

1. Orthostatic Protein Measurement 24-Hour Urine: Patient Collection Instructions in Special Instructions

2. If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.

Secondary ID

614360

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 to 4 days

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