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Test Code LAB4105 FRACTIONAL EXCRETION OF SODIUM

Important Note

**No Blood Creatinine or Blood Sodium collection will be requested for patients that have had a Blood Creatinine or Blood Sodium result in the past 24 hours.**

Specimen Type

BLOOD
Preferred Sample: Lithium Heparin Plasma (Mint Green Top, Dark Green Top)
Alternative Sample: Serum (SST, Gold, Corvac, Tiger, Red Top Tube)

URINE
Preferred Specimen: Transparent Red Top Tube
Alternative Specimen: Yellow Urine Tube, Sterile Container

Specimen Volume

2 mL Plasma/Serum
10 mL Urine

Minimum Volume

1 mL Plasma/Serum
5 mL Urine

Turnaround Time

STAT: 1 hour
Routine: 4 hours

Test Schedule

Daily

Sample Stability

Room Temp: 14 days
Refrigerated: 14 days

Method

ISE (Ion Selective Electrode), Calculation

Reference Ranges

Prerenal Intrinsic Renal Postrenal Ur Sodium < 20 > 40 > 40 FENa < 1% > 1% > 4% Prerenal: Anything that causes decreased effective renal perfusion: Hypovolemia, CHF, Renal Artery Stenosis, Sepsis, etc. Remember, contrast-induced nephropathy will often look pre-renal Intrinsic Renal: ATN, AIN, Glomerulohephritides, etc Postrenal: Obstruction (BPH, bladder stone, bilateral ureter obstruction)

CPT Codes

82565, 82570, 84295, 84300

Test Components

Sodium, Creatinine, Random Urine Sodium, Random Urine Creatinine, Fractional Excretion of Sodium

Collection Instructions

Both plasma and random urine should be obtained