A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # |
Urea Clearance
MessageTest Code
Alias/See Also
CPT Codes
84545<br /> <strong>When test is performed by Quest Diagnostics – West Hills:<br /> ** This test is not available for Florida, Maryland, New York, Pennsylvania or Rhode Island patient testing. ** </strong>
Includes
Urea Nitrogen, 24 Hour Urine
Urea Clearance (calculation)
CPT code 81050 may be added at an additional charge for volume measurement
Preferred Specimen
1 mL serum
Minimum Volume
Other Acceptable Specimens
Instructions
Aliquot from a well-mixed 24-hour collection. Record total volume on both the transport container and the test requisition.
Transport Container
Serum or plasma: Transport tube
Transport Temperature
Serum or plasma: Room temperature
Specimen Stability
Room temperature: 24 hours
Refrigerated: 7 days
Frozen: Indefinitely
Serum and plasma
Room temperature: 7 days
Reffigerated: 5 days
Frozen: 28 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Methodology
Spectrophotometry (SP)
Reference Range
Male (mg/dL) |
Female (mg/dL) |
||||
<1 Month | 4-12 | 3-17 | |||
1-11 Months | 2-13 | 4-14 | |||
1-3 Years | 3-12 | 3-14 | |||
4-19 Years | 7-20 | 7-20 | |||
≥20 Years | 7-25 | 7-25 |
Urea Nitrogen, 24 Hour Urine | 6-17 g/24 h |
Urea Nitrogen Clearance | 41-68 mL/min |
Clinical Significance
This test estimates urea clearance based on the measurements of urea nitrogen levels in a blood specimen and a 24-hour urine specimen [1]. Urea clearance may be helpful in screening for chronic kidney disease and predicting glomerular filtration rate (GFR) in patients with advanced kidney dysfunction [1].
Urea is the main nitrogen-containing product of protein breakdown, and approximately 90% of the urea excretion is through the kidneys. In individuals with normal kidney function, urea clearance is roughly half of creatinine clearance owing to tubular back-diffusion of urea to blood and making it a poor alternative to assess kidney function [1]. Averaging creatinine clearance and urea clearance is also not recommended for this purpose owing to its inferior performance [2]. However, in patients with advanced kidney dysfunction, as the urea back-diffusion decreases urea clearance may better reflect GFR [1].
Blood urea levels, commonly expressed by the concentration of blood urea nitrogen (BUN), may be increased in individuals on a high-protein diet or with increased protein breakdown, gastrointestinal hemorrhage, chronic heart failure, or treatment with cortisol [2]. BUN level may be decreased in individuals with low-protein diet and end-stage liver disease [2].
Urinary urea levels, commonly expressed by the concentration of urinary urea nitrogen, may be increased in individuals with hyperthyroidism or excess protein intake or breakdown [3]. Urinary urea nitrogen level may be decreased in individuals with malnutrition, kidney damage or insufficiency, low-protein and high-carbohydrate diet, or liver disease. Pregnant persons and healthy children may also have low urinary nitrogen levels [3].
The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.
References
1. Oh MS, et al. Evaluation of renal function, water, electrolytes, and acid-base balance. In: McPherson RA, et al, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021
2. Lamb EJ, et al. Kidney function tests. Rifai N, et al. eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elservier Inc; 2022
3. Rao LV, et al. Laboratory tests. In: Rao LV, eds. Wallach's Interpretation of Diagnostic Tests. Pathways to Arriving at a Clinical Diagnosis. 11th ed. Wolters Kluwer; 2020.
Performing Laboratory
Quest Diagnostics - West Hills
8401 Fallbrook Avenue
West Hills, CA 91304