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Test ID: MOLUC    
Molybdenum/Creatinine Ratio, Urine

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Useful For Suggests clinical disorders or settings where the test may be helpful

Monitoring of parenteral nutrition

 

Monitoring metallic prosthetic implant wear

 

As an indicator of molybdenum cofactor disease

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Molybdenum is an essential trace element found in the daily diet. It is a cofactor for some enzymes important in nitrogen metabolism (aldehyde dehydrogenase, xanthine oxidase, NADH dehydrogenase). Due to the wide distribution of molybdenum in the environment and particularly in plant materials, molybdenum deficiency is rare in adults with normal, diverse diets. Typical molybdenum intake in most geographic locations is between 45 and 90 mcg/day.(1) Urine is the primary source of excretion, though excesses are sometimes excreted by the biliary route.(2-3)

 

Molybdenum deficiency associated with parenteral nutrition is indicated by symptoms such as stunted growth, reduced appetite, tachycardia, tachypnea, blindness and coma. These symptoms can be corrected by introducing molybdenum supplementation.(3) Molybdenum cofactor disease is a severe genetic disorder that is due to defective mutations in the MOCS1, MOCS2, and GEPH genes.(4)

 

Molybdenum toxicity is rare and usually related to molybdenum mining exposure; however, it has been observed in cases of intake >400 mcg/day. Molybdenum interferes with copper uptake; molybdenum toxicity is predominantly due to copper deficiency (hypochromic anemia and neutropenia) and inhibition of xanthine oxidase (uric acid accumulation).

 

Urine molybdenum concentrations are likely to be increased above the reference range in patients with metallic joint prosthesis. Prosthetic devices produced by Zimmer Company and Johnson and Johnson typically are made of aluminum, vanadium, and titanium. Prosthetic devices produced by Depuy Company, Dow Corning, Howmedica, LCS, PCA, Osteonics, Richards Company, Tricon, and Whiteside typically are made of chromium, cobalt, and molybdenum. This List of products is incomplete, and these products change occasionally; see prothesis product information for each device for composition details.(4-5)

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

6-11 years: 70-240 mcg/g creatinine

>11 years: 40-100 mcg/g creatinine

Reference values have not been established for patients that are <6 years of age.

Interpretation Provides information to assist in interpretation of the test results

Molybdenum excretion rates are variable and related to dietary intake. Evaluation of 124 healthy adults by Mayo Clinic suggested a reference range of 6 to 190 mcg/L. The National Health and Nutrition Examination Survey (NHANES) study reported urine molybdenum ranged from 20 to 180 mcg/L. (Note: NHANES also reported excretion per gram of creatinine as 40-100 mcg/gm creatinine in adults and 70-240 mcg/gm creatinine in children.)

 

Prosthesis wear is known to result in increased circulating concentration of metal ions.(5-7) No increase (6-190 mcg/L) in urine molybdenum concentration is evident with a prosthetic device in good condition. Urine concentrations >200 mcg/L in a patient with molybdenum-based implant suggest significant prosthesis wear. Increased urine trace element concentrations in the absence of corroborating clinical information do not independently predict prosthesis wear or failure.

 

Urine molybdenum <6 mcg/L indicates potential deficiency.

 

Increased urine molybdenum may be seen in acute viral hepatitis, chronic active hepatitis, alcoholic liver disease, and other forms of liver inflammation.(2)

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Molybdenum is a trace metal commonly used in alloys and readily present in the environment. Thus, contamination of the specimen must be avoided. Failure to use metal-free collection procedures and devices may cause falsely increased results. See Specimen Required for collection and processing information.

 

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.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Third National Report on Exposure to Environmental Chemicals (NHANES). NCEH Publication 05-0570. Department of Human Service, Centers for Disease Control and Prevention. July 2005

2. Tsalev DL, Zaprianov ZK: Atomic Absorption Spectrometry in Health Practice, CRC Press, 1984

3. Shenkin A, Baines M, Fell GS, Lyon TDG: Vitamins and trace elements. In Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Edited by CA Burtis, ER Ashwood, DE Bruns. St. Louis, Elsevier Saunders, 2006, p 1132

4. Reiss J, Johnson J: Mutations in the molybdenum cofactor biosynthetic genes MOCS1, MOCS2, and GEPH. Hum Mutat 2003;21:569-576

5. Liu TK, Liu SH, Chang CH, Yang RS: Concentration of metal elements in the blood and urine in the patients with cementless total knee arthroplasty. Tohoku J Exp Med 1998;185:253-262

6. Lhotka C, Szekes T, Stefan I, et al: Four-year study of cobalt and chromium blood levels in patients managed with two different metal-on-metal total hip replacements. J Orthop Res 2003;21:189-195

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test