- 1Department of Clinical Biochemistry, The Ipswich Hospital, Ipswich, UK
- 2Department of Clinical Biochemistry, The Lister Hospital, Stevenage, UK
- 3The Medical Toxicology Unit Laboratory, Guy’s & St Thomas’ Hospital Trust, London, UK
- 4Department of Chemical Pathology, Queen’s Hospital, Burton-on-Trent, UK
- 5Department of Chemical Pathology, St Thomas’ Hospital, London, UK
- Correspondence to:
Dr P J Twomey
The Ipswich Hospital, Heath Road, Ipswich IP4 5PD, UK;
- Accepted 3 August 2006
Investigation of copper status can be a diagnostic challenge. The non-caeruloplasmin-bound copper (NCC) has deficiencies; accordingly, the copper:caeruloplasmin ratio has been suggested as an alternative index of copper status. A reference interval for this index was derived. In addition to making the interpretation of copper easier, the copper:caeruloplasmin ratio should also enable adjustment for relatively high caeruloplasmin concentrations without recourse to producing gender- and age-derived intervals. The copper:caeruloplasmin ratio has weaknesses similar to those identified for NCC in that immunological methods used for caeruloplasmin can cross react with apocaeruloplasmin and there is no standardised method for caeruloplasmin. Caeruloplasmin assays also have uncertainty from precision, bias and specificity and, accordingly, method-related differences may have a large effect on the copper:caeruloplasmin ratio in a manner similar to the NCC.
Competing interests: None declared.