A timed 24-hour urine collection is the preferred specimen for measuring and interpreting this urinary analyte. Random collections normalized to urinary creatinine may be of some clinical use in patients who cannot collect a 24-hour specimen, typically small children.
The mean urinary citrate excretion rate in patients with idiopathic calcium urolithiasis has been found to be significantly lower than that of control groups. Hypocitraturia is common in patients with urolithiasis resulting from renal tubular acidosis and in patients with enteric hyperoxaluria. Citrate excretion is low in renal insufficiency.
Transfer sample to a Urine Monovette with pH stabilizer
If a Urine Monovette with pH stabilizer is unavailable, transfer the specimen to a Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp) and freeze
Specimen preserved in Urine Monovette with pH stabilizer
Refrigerated (preferred) - 14 days
Ambient - 14 days
Frozen - 14 days
Freeze/thaw cycles - Stable x3
Frozen (strict) - 14 days
Spectrophotometry (kinetic at 340 nm)
|Gender||Age (years)||Range (mg/L)|
|Male||<40||9 - 864|
|≥40||7 - 1130|