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Test Code GDCRU Gadolinium/Creatinine Ratio, Random, Urine

Reporting Name

Gadolinium/Creat Ratio, Random, U

Useful For

Assessing chronic exposure and monitoring effectiveness of dialysis in a random urine collection

Profile Information

Test ID Reporting Name Available Separately Always Performed
GDCR Gadolinium/Creat Ratio, U No Yes
CDCR Creatinine Conc No Yes

Method Name

GDCR: Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)

CDCR: Enzymatic Colorimetric Assay

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Urine


Specimen Required


Patient Preparation: High concentrations of gadolinium and iodine are known to interfere with most metals tests. If either gadolinium- or iodine-containing contrast media has been administered, a specimen should not be collected for 96 hours.

Supplies: Urine Tubes, 10 mL (T068)

Collection Container/Tube: Clean, plastic urine collection container

Submission Container/Tube: Plastic, 10-mL urine tube (T068) or clean, plastic aliquot container with no metal cap or glued insert

Specimen Volume: 3 mL

Collection Instructions:

1. Collect a random urine specimen.

2. See Trace Metals Analysis Specimen Collection and Transport in Special Instructions for complete instructions.


Specimen Minimum Volume

0.7 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Refrigerated (preferred) 28 days
  Ambient  28 days
  Frozen  28 days

Reject Due To

Hemolysis

NA

Lipemia

NA

Icterus

NA

Other

NA

Reference Values

0-17 years: not established

≥18 years: <0.8 mcg/g creatinine

Day(s) and Time(s) Performed

Wednesday; 8 a.m.

CPT Code Information

83018-Gadolinium Concentration

82570-Creatinine Concentration

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GDCRU Gadolinium/Creat Ratio, Random, U In Process

 

Result ID Test Result Name Result LOINC Value
CDCR Creatinine Conc 2161-8
32873 Gadolinium/Creat Ratio, U Unable to Verify

Test Classification

See Individual Test IDs

Method Description

Gadolinium (Gd) is analyzed by inductively coupled plasma-mass spectrometry in standard mode using terbium (Tb) as an internal standard and a plasma matrix calibration.(Leung N, Pittelkow MR, Lee CU, et al: Chelation of gadolinium with deferoxamine in a patient with nephrogenic systemic fibrosis. NDT Plus 2009;2[4]:309-311)

 

Creatinine enzymatic method is based on the determination of sarcosine from creatinine with the aid of creatininase, creatinase, and sarcosine oxidase. The liberated hydrogen peroxide is measured via a modified Trinder reaction using a colorimetric indicator. Optimization of the buffer system and the colorimetric indicator enables the creatinine concentration to be quantified both precisely and specifically.(Package insert: Roche Diagnostics, Indianapolis IN, 2004)

Analytic Time

1 day

Specimen Retention Time

14 days

Clinical Information

Gadolinium is a member of the lanthanide series of the periodic table of elements and is considered a nonessential element. Due to its paramagnetic properties, chelated gadolinium is commonly employed as contrast media (gadolinium-based contrast agents: GBCA) for magnetic resonance imaging and computer tomography scanning.

 

Gadolinium is primarily eliminated via the kidneys, so exposure can be prolonged in patients with renal insufficiency. In healthy subjects with normal renal function, the plasma half-life of gadolinium is approximately 90 minutes (1.5 hours). Patients with reduced renal function and some patients with normal renal function may exhibit a prolonged gadolinium elimination half-life.

 

To date, the only known adverse health effect related to gadolinium retention is a rare condition called nephrogenic systemic fibrosis (NSF). NSF is a relatively uncommon condition in which fibrous plaques develop in the dermis and, often, in deeper connective tissues. Reported cases have occurred almost exclusively in patients with severe renal disease, and almost all have been associated with prior use of GBCA. NSF is a painful skin disease characterized by thickening of the skin, which can involve the joints and cause significant limitation of motion within weeks to months. Over the past decade, changes in clinical practice guidelines have almost completely eliminated the incidence of NSF. However, the association of NSF and observed elevated gadolinium concentrations is still not fully understood.

Interpretation

Elevated urine gadolinium results collected more than 96 hours after administration of a gadolinium-based contrast agent only confirms past exposure, or continued exposure through anthropogenic sources, and prolonged elimination of gadolinium. Gadolinium also has been shown to be present in some municipal water sources, which may contribute to the observation of low concentrations of gadolinium in patients who never have been exposed to gadolinium-based contrast agents (GBCA).

 

Elevated gadolinium in a specimen collected more than 96 hours after contrast media infusion does not indicate risk of nephrogenic systemic fibrosis (NSF).

Cautions

Urine gadolinium concentration will be elevated if the specimen is collected less than 96 hours after administration of gadolinium-based contrast agents (GBCA). This elevation is due to the residual gadolinium present from contrast media infusion. An elevated gadolinium in a specimen collected more than 96 hours after contrast media infusion does not definitively indicate risk of nephrogenic systemic fibrosis (NSF) or gadolinium toxicity. Ultimately, patients should consult with their healthcare providers to interpret any test results.

 

Gadolinium may also be present in the effluent of metropolitan sewage treatment plants and in the rivers near metropolitan areas. Sewage treatment does not remove gadolinium. Anthropogenic sources of gadolinium could contribute to low concentrations of gadolinium excreted in the urine.