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Oxalic Acid, Adult, Urine with Creatinine [10456X]
Test Code14467
CPT Codes
82570, 83945
Preferred Specimen
10 mL urine preserved with 6N HCl, submitted in a sterile leak-proof container
Patient Preparation
Patient should refrain from taking excessive amounts Ascorbic Acid or Oxalate-rich foods (i.e., spinach, coffee, tea, chocolate, rhubarb) for at least 48 hours before the collection period.
Minimum Volume
2 mL
Other Acceptable Specimens
Unpreserved urine, or added preservative after collection
Instructions
Adjust pH to < 3.0 with 6N HCl before aliquoting for testing.
For Pediatric patients: order test code 11222-Oxalic Acid, Pediatric, Urine w/Creatinine. Add 2 mL 6N HCL per 100 mL Urine.
For Pediatric patients: order test code 11222-Oxalic Acid, Pediatric, Urine w/Creatinine. Add 2 mL 6N HCL per 100 mL Urine.
Transport Container
Sterile leak-proof container
Transport Temperature
Room temperature
Specimen Stability
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 24 days
Refrigerated: 7 days
Frozen: 24 days
Methodology
Spectrophotometric
Setup Schedule
Set up: Tues-Sat; Report available: 1-3 days
Reference Range
See Laboratory Report
Clinical Significance
This quantitative oxalic acid test, performed with a random urine specimen, may help screen for hyperoxaluria, determine the cause of kidney stones, and assess kidney function in adults [1]. However, 24-hour urine specimens are generally preferred to random specimens when measuring oxalic acid for diagnostic evaluation and monitoring of hyperoxaluria [1,2].
Oxalic acid is an organic compound that naturally exists in many food sources. Because humans cannot metabolize oxalic acid, it must be excreted in urine as oxalate (the ionic form of oxalic acid). Excessive excretion of oxalates is called hyperoxaluria and can be attributed to primary or secondary causes. Primary hyperoxaluria (PH) is a rare condition resulting from enzymatic defects and can lead to chronic kidney disease, which may progress to kidney failure. Secondary hyperoxaluria can be caused by fat malabsorption, which may be due to inflammatory bowel disease, extensive resection of the small bowel, or excessive ingestion of substances that increase serum oxalates [3].
PH is associated with significant morbidity and mortality, including end-stage kidney disease [1]. Early diagnosis is associated with better outcomes, but more than 40% of PH diagnoses are delayed [1]. Screening for PH may be considered for adults with recurrent calcium oxalate stones or family history of stone disease [1].
Urinary oxalic acid measurements may be inaccurate when estimated glomerular filtration rate declines [1]. Therefore, in patients with chronic kidney disease, plasma oxalate may be measured to help support the diagnosis of PH [1].
Results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.
References
1. Bhasin B, et al. World J Nephrol. 2015;4(2):235-244.
2. Williams JC Jr, et al. Urolithiasis. 2021;49(1):1-16.
3. Shchelochkov O, et al. Defects in metabolism of amino acids. In: Kliegman R, et al. Nelson Textbook of Pediatrics. 21st ed. Elsevier; 2019:720-722.
Oxalic acid is an organic compound that naturally exists in many food sources. Because humans cannot metabolize oxalic acid, it must be excreted in urine as oxalate (the ionic form of oxalic acid). Excessive excretion of oxalates is called hyperoxaluria and can be attributed to primary or secondary causes. Primary hyperoxaluria (PH) is a rare condition resulting from enzymatic defects and can lead to chronic kidney disease, which may progress to kidney failure. Secondary hyperoxaluria can be caused by fat malabsorption, which may be due to inflammatory bowel disease, extensive resection of the small bowel, or excessive ingestion of substances that increase serum oxalates [3].
PH is associated with significant morbidity and mortality, including end-stage kidney disease [1]. Early diagnosis is associated with better outcomes, but more than 40% of PH diagnoses are delayed [1]. Screening for PH may be considered for adults with recurrent calcium oxalate stones or family history of stone disease [1].
Urinary oxalic acid measurements may be inaccurate when estimated glomerular filtration rate declines [1]. Therefore, in patients with chronic kidney disease, plasma oxalate may be measured to help support the diagnosis of PH [1].
Results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.
References
1. Bhasin B, et al. World J Nephrol. 2015;4(2):235-244.
2. Williams JC Jr, et al. Urolithiasis. 2021;49(1):1-16.
3. Shchelochkov O, et al. Defects in metabolism of amino acids. In: Kliegman R, et al. Nelson Textbook of Pediatrics. 21st ed. Elsevier; 2019:720-722.
