Evaluation of hypo- or hyper-phosphatemic states
Evaluation of patients with nephrolithiasis
Molybdic Acid
Phosphate
PO4
Urine
Question ID | Description | Answers |
---|---|---|
TM12 | Collection Duration | |
VL10 | Urine Volume |
Supplies: Sarstedt 5 mL Aliquot Tube (T914)
Collection Container/Tube: 24-Hour graduated urine container with no metal cap or glued insert
Submission Container/Tube: Plastic, 5 mL tube or a clean, plastic aliquot container with no metal cap or glued insert
Specimen Volume: 4 mL
Collection Instructions:
1. Collect urine for 24 hours.
2. Refrigerate specimen within 4 hours of completion of 24-hour collection.
Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens for multiple collections.
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.
Note: The addition of preservative or application of temperature controls must occur within 4 hours of completion of the collection.
Ambient | OK |
Refrigerate | Preferred |
Frozen | OK |
50% Acetic Acid | OK |
Boric Acid | OK |
Diazolidinyl Urea | OK |
6M Hydrochloric Acid | OK |
6M Nitric Acid | No |
Sodium Carbonate | No |
Thymol | OK |
Toluene | No |
1 mL
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability. |
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Urine | Refrigerated (preferred) | 14 days | |
Frozen | 30 days | ||
Ambient | 7 days |
Evaluation of hypo- or hyper-phosphatemic states
Evaluation of patients with nephrolithiasis
Approximately 80% of filtered phosphorus is reabsorbed by renal proximal tubule cells. The regulation of urinary phosphorus excretion is principally dependent on regulation of proximal tubule phosphorus reabsorption. A variety of factors influence renal tubular phosphate reabsorption and consequent urine excretion. Factors that increase urinary phosphorus excretion include high phosphorus diet, parathyroid hormone, extracellular volume expansion, low dietary potassium intake, and proximal tubule defects (eg, Fanconi Syndrome, X-linked hypophosphatemic Rickets, tumor-induced osteomalacia). Factors that decrease, or are associated with decreases in, urinary phosphorus excretion include low dietary phosphorus intake, insulin, high dietary potassium intake, and decreased intestinal absorption of phosphorus (eg, phosphate-binding antacids, vitamin D deficiency, malabsorption states).
A renal leak of phosphate has also been implicated as contributing to kidney stone formation in some patients.
> or =18 years: 226-1,797 mg/24 hours
Reference values have not been established for patients who are less than 18 years of age.
Interpretation of urinary phosphorus excretion is dependent upon the clinical situation, and should be interpreted in conjunction with the serum phosphorus concentration.
No significant cautionary statements
1. Delaney MP, Lamb EJ: Kidney disease. In: Rifai N, Horvath AR, Wittwer CT, eds: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:1280-1283
2. Agarwal R, Knochel JP: Hypophosphatemia and hyperphosphatemia. In: Brenner BM, ed. The Kidney. 6th ed. WB Saunders Company; 2000:1071-1125
Inorganic phosphorus reacts with ammonium molydbdate in an acidic solution to form ammonium phosphomolybdate. The ammonium phosphomolybdate is quantified in the ultraviolet range (340 nm).(Package insert: Roche Phosphorus. Roche Diagnostics; V9.0 12/2019)
Monday through Sunday
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.
84105
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
POU | Phosphorus, 24 HR, U | 2779-7 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
---|---|---|
POUU | Phosphorus, 24 HR, U | 2779-7 |
TM12 | Collection Duration | 13362-9 |
VL10 | Urine Volume | 3167-4 |
PHOCN | Phosphorus Concentration | 21458-5 |