Protein, Total, Urine
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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(s) (eg, multiple myeloma, myoglobinuria)
-Urinary tract inflammation or tumor
Evaluation of renal disease
Screening for monoclonal gammopathy
Total protein >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.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Increased urine protein levels (false-positives) may be due to contamination of urine with menstrual blood, prostatic secretions, or semen.
Protein electrophoresis and immunofixation may be required to characterize and interpret the proteinuria.
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.
> or =18 years: <102 mg/24 hours
Reference values have not been established for patients that are <18 years of age.
Reference value applies to 24-hour collection.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
Keren DF: Clinical indications for electrophoresis and immunofixation. In Manual of Clinical Laboratory Immunology. Fifth edition. Edited by NR Rose, E Conway de Macario, JD Folds, et al. Washington, DC, ASM Press, 1997, pp 65-74