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Chromium (Cr) exists in valence states ranging from 2(-) to 6(+). Hexavalent chromium (Cr[+6]) and trivalent chromium (Cr[+3]) are the 2 most prevalent forms. Cr(+6) is used in industry to make chromium alloys including stainless steel, pigments, and electroplated coatings. Cr(+6), a known carcinogen, is immediately converted to Cr(+3) upon exposure to biological tissues. Cr(+3) is the only chromium species found in biological specimens.
Serum Cr concentrations are likely to be increased above the reference range in patients with metallic joint prosthesis. 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 prosthesis product information for each device for composition details.
Screening for occupational exposure
Monitoring metallic prosthetic implant wear
Results greater than the flagged value indicate clinically significant exposure to chromium (Cr) (see Cautions about specimen collection).
Prosthesis wear is known to result in increased circulating concentration of metal ions. Modest increase (0.3-0.6 ng/mL) in serum Cr concentration is likely to be associated with a prosthetic device in good condition. Serum concentrations >1 ng/mL in a patient with Cr-based implant suggest significant prosthesis wear. Increased serum trace element concentrations in the absence of corroborating clinical information do not independently predict prosthesis wear or failure.
Specimens from unexposed individuals collected using metal-free collection procedures typically have chromium >0.3 ng/mL. Chromium is present in our environment at 100-fold to 1,000-fold higher concentration than found in biological tissues. Reports of increased serum chromium could be due to external contamination. Metal-free serum collection procedures must be followed, and centrifuged serum must be aliquoted into a Mayo Medical Laboratories metal-free vial to avoid external contamination. Specimens collected using an anticoagulant are unacceptable; trace amounts of chromium are present in anticoagulants used in evacuated collection tubes.
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 cannot be collected for 96 hours.
When collected by a phlebotomist experienced in ultra-clean collection technique and handled according to the instructions in Trace Metals Analysis Specimen Collection and Transport in Special Instructions, we have observed the concentration of chromium in serum to be <0.3 ng/mL. However, the majority of specimens submitted for analysis from unexposed individuals contain 0.3 ng/mL to 0.9 ng/mL of chromium. Commercial evacuated blood collection tubes not designed for trace-metal specimen collection yield serum containing 2.0 ng/mL to 5.0 ng/mL chromium derived from the collection tube.
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2. NIOSH Hexavalent Chromium Criteria Document Update. September 2008; Available from URL: http://www.cdc.gov/niosh/topics/hexchrom/
3. Keegan GM, Learmonth ID, Case CP: A systematic comparison of the actual, potential, and theoretical health effects of cobalt and chromium exposures from industry and surgical implants. Crit Rev Toxicol 2008;38:645-674
4. Tower SS: Arthroprosthetic cobaltism: Neurological and cardiac manifestations in two patients with metal-on-metal arthroplasty: A case report. J Bone Joint Surg Am 2010;92:1-5