SHORT REPORT

Copper:caeruloplasmin ratio

Patrick J Twomey¹, Adie Viljoen², Ivan M House³, Timothy M Reynolds⁴, Anthony S Wierzbicki⁵

¹ Department of Clinical Biochemistry, The Ipswich Hospital, Ipswich, UK
² Department of Clinical Biochemistry, The Lister Hospital, Stevenage, UK
³ The Medical Toxicology Unit Laboratory, Guy’s & St Thomas’ Hospital Trust, London, UK
⁴ Department of Chemical Pathology, Queen’s Hospital, Burton-on-Trent, UK
⁵ Department of Chemical Pathology, St Thomas’ Hospital, London, UK

Correspondence to:
Correspondence to:
Dr P J Twomey
The Ipswich Hospital, Heath Road, Ipswich IP4 5PD, UK; patrick.twomey{at}ipswichhospital.nhs.uk

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.

Abbreviations: NCC, non-caeruloplasmin-bound copper

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