Molecular Weight of Copper (Cu): 63.54 grams
copper not bound to ceruloplasmin in µg/dL =
= (total serum copper in µg/dL) – (3 * (serum ceruloplasmin in mg/dL))
copper not bound to ceruloplasmin in µmol/L =
= (total serum copper in µmol/L) – (0.047 * (serum ceruloplasmin mg/L))
where:
• 3 is in µg copper bound per mg ceruloplasmin
• 0.047 is µmol copper bound per mg ceruloplasmin
• To convert µg/dL to µmol/L, multiply by 10 / 63.54 = 0.1574
Interpretation:
• The normal nonbound serum copper is 0 – 10 µg/dL.
• Toxic levels of copper are associated with increased nonbound serum copper.
• In Wilson's disease, the amount of nonbound serum copper is increased.
Limitations:
• The blood samples need to be collected correctly in a plastic vial or metal free tube to prevent falsely elevated serum values.
NOTE: According to Tietz NW, Clinical Guide to Laboratory Tests, Third Edition, 1995, page 168, normal plasma copper is about 80% of the serum levels for males and 90% of the serum levels for females.
