Scottish Trace Element & Micronutrient Reference Laboratory

Scotland's specialised laboratory for trace elements and vitamins in health and disease

Copper (Cu)

Copper is an essential component of numerous copper metalloenzymes that are required for normal oxidative metabolism, iron metabolism, free radical detoxification and synthesis of haemoglobin, elastin and collagen. Only small amounts of copper are required in the diet (1.0 mg/day). Copper is absorbed in the proximal intestine. Copper is normally excreted in bile and so an increase in plasma and urine copper may occur in cholestatic liver disease. Most circulating copper is in the form of caeruloplasmin. Oestrogens increase copper by increasing caeruloplasmin synthesis, so it can be two to three-fold higher in the last trimester of pregnancy and with the use of oral contraceptives. In neonates, copper is low (3-5 µmol/L) but increases gradually to adult values by one year of age. For this reason copper deficiency may occur especially in neonates on diets deficient in copper and they are at potential risk of bone disease. Plasma copper is sometimes requested when abuse is suspected in young children with unexplained bone fracture.


Copper deficiency is uncommon but may occur as a result of gastric surgery, untreated coeliac disease, misplaced duodenal tube and, more commonly, inhibition of its absorption because of high oral zinc ingestion (usually in excess of 75 mg/day) following zinc prescription or over-the-counter purchase of zinc supplements, high zinc enteral feeds, or over-application of zinc-containing dental adhesive (Fixodent). Symptoms are anaemia, neutropenia and in more severe cases ataxia and peripheral neuropathy.


Measurement of copper is centrally involved in the diagnosis of Wilson's Disease. Concentrations are usually low in plasma because of the impairment of its incorporation into caeruloplamin, the main copper carrying protein in the circulation, and high in urine and liver. Liver concentrations of over 250 µg/g dry weight are usually found. However, 3% of Wilson’s Disease patients have results < 50 µg/g and 13% of Wilson’s Disease patients have results of 50 to 250 µg/g.26 High concentrations may also be found in obstructive liver disease.26 A more reliable and safer follow-up test is the measurement of copper uptake using the stable isotope 65Cu details of which are available from the laboratory (More details and protocol for this test).

Other rarer genetic causes of a low plasma copper are Menkes Disease and acaeruloplasminaemia.

Assessment of Status

Caeruloplasmin, and so copper, is a positive acute phase reactant and a detectable increase in plasma copper (by up to 30%) may be seen after infection, injury, or inflammation. In the first two days following elective surgery, plasma copper falls by around 10% (Table 1).27 Subsequently copper concentrations increase by up to 25% (Table 2).28 Occasionally in patients with a severe systemic inflammatory response plasma copper concentrations may fall substantially.

Recommended Daily Allowance

Adults: 1 mg/day.

 

Effect of Systemic Inflammatory Response on Plasma Copper Concentrations

Table 1: Baseline, peak/ trough and day 7 concentrations of plasma copper following elective surgery for knee arthroplasty (n = 20)27.

Analyte Baseline values

Peak/trough

(48 h)

Final values

(168 h)

Friedman

(0 to 168 h)

CRP (mg/L) <6 (<6–17) 160 (83-240) 29 (10-87) p < 0.001
Copper (μmol/L) 18.1 ± 4.4 16.0 ± 3.9 22.0 ± 4.6 p < 0.001

 

Table 2: Distribution of median plasma copper concentrations according to increments of CRP concentrations (n = 2176)28.

CRP

(mg/L)

n

Median Cu

(μmol/L)

p
≤ 5 1133 16.1 -
> 5 to 10 309 18.4 <0.001
> 10 to 20 227 19.8 <0.001
> 20 to 40 174 20.6 <0.001
> 40 to 80 142 19.3 <0.001
> 80 191 18.8 <0.001

 

Further Information

Wilson's Disease Information Site

Food Standards Agency on Copper

 

Sample Requirements and Reference Ranges for Copper

Sample Type Plasma /serum (fasting sample preferred), urine (24 hour sample)*, liver biopsy
Container Plasma/serum: lithium heparin (non-gel), plain, or ‘Trace Metal’.  SST, lithium heparin gel and EDTA tubes are unsuitable.
Urine*: 24 h urine container. Acid-washed container not necessary.
Liver: universal container
Precautions Plasma/serum: Send by first class post within 48 hours.
If delivery to Glasgow is outwith 48 hours of sample collection. Centrifuge sample and send plasma/serum.
Please mix 24 hour urine well before taking an aliquot and quote 24 h urine volume on request form.
Liver biopsy: Samples should be transferred directly to the wall of a Universal container; please do not put onto lint or use preservative. It should be stored frozen but can be mailed at room temperature.
Minimum volume** Plasma: 250 μL (zinc and selenium can be analysed simultaneously on this volume)
Urine: 1 mL
Liver biopsy: 1 mg (results are an approximation if biopsy weight <5 mg)

Reference ranges

Plasma (µmol/L):                  10 to 22              (men; STEMDRL derived)
                                            11 to 25              (women; STEMDRL derived))
                                            27 to 49              (pregnancy)
                                            1.5 to 7.0            (0 to 3 months)29
                                            4.0 to 17.0          (3 to 6 months)29
                                            8.0 to 20.5          (6 to 12 months)29
                                            12.5 to 23.5        (1 to 5 years)29
                                            13.0 to 21.5        (6 to 9 years)29
                                            12.5 to 19.0        (10 to 13 years)29            

Urine copper:                       < 0.6 µmol/24h   (STEMDRL derived)***

Liver:                                    8 to 40 µg/g dry weight30
                                             > 250 µg/g dry weight (consistent with, but not

                                             diagnostic for Wilson's disease)  

Mean Turnaround time Plasma / serum: 2.6 days; urine: 4.5 days
Method Inductively coupled plasma mass spectrometry
Traceability Plasma: Traceable to reference material produced in accordance with EN ISO 17511:2003 “In vitro diagnostic medical devices. Measurement of quantities in biological samples. Metrological traceability of values assigned to calibrators and control materials”
Urine: Traceable to reference material produced in accordance with EN ISO 17511:2003 “In vitro diagnostic medical devices. Measurement of quantities in biological samples. Metrological traceability of values assigned to calibrators and control materials” and reference materials with values determined by reference laboratories.
Liver: Traceable to certified reference material BCR 185R and ERM – BB186.
Intermediate Precision (CV) Plasma:    2.4% at 10.0 µmol/L, 1.9% at 16.2 µmol/L
Urine:       8.9% at 0.8 µmol/L, 11.0% at 1.4 µmol/L
Liver:        6.7% at 31.8 µg/g, 5.1% at 186 µg/g
Measurement Uncertainty, U Plasma:    10.0 ± 0.5 µmol/L, 16.2 ± 0.6 µmol/L
Urine:       0.8 ± 0.1 µmol/L, 1.4 ± 0.3 µmol/L
Liver:        31.8 ± 4.3 µg/g, 186 ± 18.9 µg/g
Analytical Goals (CV)

Plasma: Acceptable 6.0%, Desirable 4.0****. Urine: 8%*****.

Liver: 10%*****

EQA Scheme Plasma, urine and liver: UK NEQAS, Guildford

* A 24 hour sample is required, unless request is part of a penicillamine test. Please quote volume of timed collection. If a volume is not quoted the sample will be assumed to be random and analysis not performed.
** Absolute minimum volume; this volume is insufficient to carry out repeat analysis if analysis fails.
*** 0.6 µmol/24h is also the cut-off quoted in Wilson’s Disease guidelines.31
**** Goal origin: biological variation.32,33,34   ***** Goal Origin: STEMDRL state-of-the-art

 

References

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