Test Details
Methodology
Nuclear magnetic resonance (NMR) or Enzymatic
Result Turnaround Time
2 - 7 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Use
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.
Special Instructions
Record entire 24-hour total volume on the request form. pH must be 1 to 3 or the sample frozen without the addition of acid.
Limitations
This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.
Specimen Requirements
Specimen
Urine (24-hour), acidified or frozen
Volume
2 mL aliquot
Minimum Volume
1 mL aliquot (Note: This volume does not allow for repeat testing.)
Container
Plastic Labcorp 24-hour urine container with 30 mL 6N HCl preservative (Labcorp No. 21584)
Collection Instructions
Collect 24-hour urine with 30 mL 6N HCl. Caution: Strong acid. Mix well. Instruct the patient to void at 8 a.m. and discard the specimen. Then collect all urine including the final specimen voided at the end of the 24-hour collection period (i.e., 8 a.m. the next morning). Screw the lid on securely. Container must be labeled with patient's full name and date and time collection started and finished. Keep container refrigerated during collection. Preservative is not necessary during collection but should be added to urine collection within 24 hours. Final pH must be 1 to 3. Measure and record on the request form 24-hour total volume and send aliquot to the laboratory. Alternatively, the sample may be frozen without added acid.
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 29 days |
Refrigerated | 29 days |
Frozen | 49 days |
Freeze/thaw cycles | Stable x5 |
Reference Range
320−1240 mg/24 hours
Storage Instructions
Refrigerate at 2°C to 8°C after collection.
Causes for Rejection
Citrate: Boric Acid used as a preservative (Boric acid ≥1250 mg/dL may cause citrate results to be reduced by approximately 30%); multivitamin ≥397.5 mg/dL (estimated as 1 pill per day) may cause citrate results to be unmeasurable. Results of interference testing may not be representative of in-vivo characteristics of multivitamin consumption.
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 016865 | Citric Acid (Citrate), Urine | 016866 | Citric Acid, Urine | mg/L | 21203-5 | |
| 016865 | Citric Acid (Citrate), Urine | 016867 | Citric Acid, U, 24hr | mg/24 hr | 6687-8 | |
| Order Code | 016865 | |||||
| Order Code Name | Citric Acid (Citrate), Urine | |||||
| Order Loinc | ||||||
| Result Code | 016866 | |||||
| Result Code Name | Citric Acid, Urine | |||||
| UofM | mg/L | |||||
| Result LOINC | 21203-5 | |||||
| Order Code | 016865 | |||||
| Order Code Name | Citric Acid (Citrate), Urine | |||||
| Order Loinc | ||||||
| Result Code | 016867 | |||||
| Result Code Name | Citric Acid, U, 24hr | |||||
| UofM | mg/24 hr | |||||
| Result LOINC | 6687-8 |