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Test ID: OPTU    
Orthostatic Protein, Timed Collection, Urine

Useful For Suggests clinical disorders or settings where the test may be helpful

Diagnosis of orthostatic proteinuria

 

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

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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, 1 collection obtained while the person is recumbent or supine, the other when upright.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Nighttime (supine) collection: <50 mg/specimen

Daytime collection

Males: 0-150 mg/specimen

Females: 27-93 mg/specimen

Interpretation Provides information to assist in interpretation of the test results

Supine urine protein excretion <50 mg/specimen with an elevated upright or 24-hour urine collection (>150 mg for males, >93 mg for females) is considered consistent with orthostatic proteinuria.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

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 <50 mg/8 hrs.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Dodge WF, West EF, Smith EH, Harvey B: Proteinuria and hematuria in school children: Epidemiology and early natural history. J Pediatr 1976;88:327

2. Hogg RJ, Portman RJ, Milliner D, et al: Evaluation and management of proteinuria and nephritic syndrome in children. Pediatrics 2000;105:1242

3. Addis T: Prognosis in postural (orthostatic proteinuria). Forty to fifty-year follow-up of six patients after diagnosis. N Engl J Med 1981;305:618

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test