Oxalic Acid, Pediatric Urine [11222X]

Test Code

15840

CPT Codes
82570, 83945

Preferred Specimen

10 mL of 2^nd morning voided urine acidified with 6N HCl before aliquoting for testing, collected in a sterile, plastic leakproof container

Patient Preparation
Patient should refrain from taking excessive amounts of Ascorbic Acid or Oxalate-rich foods (i.e., spinach, coffee, tea, chocolate, rhubarb) for at least 48 hours before the collection period.

Minimum Volume

3 mL

Instructions

Adjust pH to < 3.0 with 6N HCl before aliquoting for testing.
Please submit second morning voided specimen

Transport Temperature

Room temperature

Specimen Stability

Room temperature: 7 days
Refrigerated: 7 days
Frozen: 24 days

Methodology
Spectrophotometry

Setup Schedule

Set up: Tues-Sat; Report available: 1-3 days

Reference Range

Age	Male (mg/mg creat)	Female (mg/mg creat)
< 1 month	Not established	Not established
1-5 months	0.05-0.18	0.05-0.18
6-11 months	0.04-0.14	0.04-0.14
1 year	0.04-0.11	0.04-0.11
2 years	0.03-0.08	0.03-0.08
3-4 years	0.02-0.07	0.02-0.07
5-6 years	0.02-0.06	0.02-0.06
7-17 years	0.01-0.05	0.01-0.05
> 17 years	<0.03	<0.04

Clinical Significance

This test is often used to screen for hyperoxaluria and assess kidney function in children. It can help to determine the cause of kidney stones and monitor treatment [1].

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 [2].

PH is associated with significant morbidity and mortality, including end-stage renal disease [1]. By itself, PH accounts for 7% to 14% of nephrocalcinosis cases among children [3]. PH is treatable. Early diagnosis is associated with better outcomes, but more than 40% of PH diagnoses are delayed [1]. The National Organization of Rare Diseases (NORD)
recommends metabolic screening of all children with nephrolithiasis or nephrocalcinosis [4].

Results from 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. Shchelochkov O, et al. Defects in metabolism of amino acids. In: Kliegman R, at al. Nelson Textbook of Pediatrics. 21st ed. Elsevier; 2019:720-722.
3. Hulton S-A. Int J Surg. 2016;36(Pt D):649-654.
4. NORD. Primary hyperoxaluria. Accessed September 2,2021.
https://rarediseases.org/rare-diseases/primary-hyperoxaluria/

Performing Laboratory
Quest Diagnostics Nichols Institute
14225 Newbrook Drive
Chantilly, VA 20153

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.