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Test Code LAB9518 Magnesium/Creatinine Ratio, Random, Urine

Additional Codes

MAGRU


Specimen Required


Supplies: Sarstedt Aliquot Tube 5 mL (T914)

Collection Container/Tube: Plastic urine container

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 a random urine specimen.

2. No preservative.


Secondary ID

621396

Useful For

Assessing the cause of abnormal serum magnesium concentrations

 

Determining whether nutritional magnesium loads are adequate

 

Calculating urinary calcium oxalate and calcium phosphate supersaturation and assessing kidney stone risk.

Profile Information

Test ID Reporting Name Available Separately Always Performed
MCTR1 Magnesium/Creat Ratio, Random, U No Yes
MGCO Magnesium, Random, U No Yes
CRETR Creatinine, Random, U No Yes

Method Name

MGCO: Colorimetric Endpoint Assay

CRETR: Enzymatic Colorimetric Assay

MCTR1: Calculation

Specimen Type

Urine

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 14 days
  Frozen  30 days
  Ambient  72 hours

Reject Due To

  All specimens will be evaluated at Mayo Clinic Laboratories for test suitability

Reference Values

1 month-<12 months: 0.10-0.48 mg/mg creat

12 months-<24 months: 0.09-0.37 mg/mg creat

24 months-<3 years: 0.07-0.34 mg/mg creat

3 years-<5 years: 0.07-0.29 mg/mg creat

5 years-<7 years: 0.06-0.21 mg/mg creat

7 years-<10 years: 0.05-0.18 mg/mg creat

10 years-<14 years: 0.05-0.15 mg/mg creat

14 years-<18 years: 0.05-0.13 mg/mg creat

18 years-83 years: 0.04-0.12 mg/mg creat

Reference values have not been established for patients who are younger than 1 month.

Reference values have not been established for patients who are older than 83 years.

Interpretation

Urinary magnesium excretion should be interpreted in concert with serum concentrations.

 

In the presence of hypomagnesemia, a 24-hour urine magnesium above 24 mg/day or fractional excretion above 0.5% suggests renal magnesium wasting. Lower values suggest inadequate magnesium intake and/or gastrointestinal losses.

 

In the presence of hypermagnesemia, urinary magnesium levels provide an indication of current magnesium intake.

 

Lower urinary magnesium excretion increases urinary calcium oxalate and calcium phosphate supersaturation and could contribute to kidney stone risk.

Method Description

Magnesium:

In alkaline solution, magnesium forms a purple complex with xylidyl blue, diazonium salt. The magnesium concentration is measured photometrically via the decrease in xylidyl blue absorbance.(Package insert: Roche MG2 kit. Roche Diagnostics; V17.0 03/2022)

 

Creatinine:

The 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: Creatinine plus ver 2. Roche Diagnostics; V2.0 03/2023)

Specimen Retention Time

7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

83735

82570

LOINC Code Information

Test ID Test Order Name Order LOINC Value
MAGRU Magnesium/Creat Ratio, Random, U 13474-2

 

Result ID Test Result Name Result LOINC Value
CRETR Creatinine, Random, U 2161-8
MGCO Magnesium, Random, U 19124-7
MCTR1 Magnesium/Creat Ratio, Random, U 13474-2

Forms

If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 to 3 days