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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

Collection Instructions

Both plasma and random urine should be obtained

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)

Test Components

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

CPT Codes

82565, 82570, 84295, 84300