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Test Code MISC2MAYOPBUCR Lead/Creatinine Ratio, Random, Urine


Ordering Guidance


The Centers for Disease Control and Prevention recommends venous blood collection for lead testing; see PBDV / Lead, Venous, with Demographics, Blood.



Specimen Required


Patient Preparation: High concentrations of gadolinium and iodine are known to interfere with most metal 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 container with no metal cap or glued insert

Submission Container/Tube: Plastic, 10-mL urine tube 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 Metals Analysis Specimen Collection and Transport for complete instructions.


Secondary ID

608908

Useful For

Detecting clinically significant lead exposure, a toxic heavy metal, using random urine specimens

Profile Information

Test ID Reporting Name Available Separately Always Performed
PBCU Lead/Creatinine Ratio, U No Yes
CRETR Creatinine, Random, U No Yes

Method Name

PBCU: Triple-Quadrupole Inductively Coupled Plasma Mass Spectrometry (ICP-MS/MS)

CRETR: Enzymatic Colorimetric Assay

Reporting Name

Lead/Creat Ratio, Random,U

Specimen Type

Urine

Specimen Minimum Volume

1.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  14 days

Reject Due To

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

Clinical Information

Increased urine lead concentration per gram of creatinine indicates significant lead exposure. Measurement of urine lead concentration per gram of creatinine before and after chelation therapy have been used as an indicator of significant lead exposure. However, the American College of Medical Toxicology (ACMT 2010) position statement on post-chelator challenge urinary metal testing states that "post-challenge urinary metal testing has not been scientifically validated, has no demonstrated benefit, and may be harmful when applied in the assessment and treatment of patients in whom there is concern for metal poisoning."

 

Blood lead measurement is the best test for clinical correlation of toxicity.

 

For more information see PBDV / Lead, Venous, with Demographics, Blood.

Reference Values

LEAD/CREATININE:

0-17 years: Not established

≥18 years: <2 mcg/g creatinine

 

CREATININE:

≥18 years: 16-326 mg/dL

Reference values have not been established for patients who are younger than 18 years of age.

Interpretation

Measurements of urinary lead (Pb) levels have been used to assess lead exposure. However, like lead blood, urinary Pb excretion mainly reflects recent exposure and thus shares many of the same limitations for assessing lead body burden or long-term exposure.(1,2)

 

Urinary lead concentration increases exponentially with blood lead and can exhibit relatively high intra-individual variability, even at similar blood lead concentrations.(3,4)

Method Description

Lead:

The metal of interest is analyzed by triple-quadrupole inductively coupled plasma mass spectrometry.(Unpublished Mayo method)

 

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; V15.0, 03/2019)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

83655

82570

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PBUCR Lead/Creat Ratio, Random,U 13466-8

 

Result ID Test Result Name Result LOINC Value
608904 Lead/Creatinine Ratio, U 13466-8
CRETR Creatinine, Random, U 2161-8

Day(s) Performed

Monday through Friday

Report Available

2 to 4 days