This guide is intended for medical, nursing and laboratory staff as an aid to making the most efficient use of the service provided by this laboratory for trace elements monitoring. It should be used in conjunction with the Handbook of the SAS Trace Elements Laboratories (Ed. Andrew Taylor. 4th Edition, Guildford 2006) which is accessible on www.sas-centre.org.
The Laboratory is CPA accredited. The Trace Elements Section has had Supraregional Assay Service (SAS) designation since 1974, and is on the list of laboratories ‘approved’ by the Health and Safety Executive for the occupational monitoring of lead and cadmium. Good practical working relationships are maintained with the other SAS Trace Element Laboratories.
Analysis is performed by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (flame and electro-thermal). Performance is monitored by extensive participation in a number of External Quality Assessment Schemes: NEQAS (blood lead and cadmium); TEQAS (eight analytes in blood, serum and urine); Quebec (eight analytes in blood, serum and urine); SAS (blood lead, serum aluminium, copper and zinc). In addition, each batch analysis is monitored by the inclusion of internal quality control materials.
The Service Offered
The
laboratory aims to provide a comprehensive advisory, analytical and
interpretational service for the following trace elements and toxic metals.
Essential
elements:
copper - plasma/serum & urine
selenium - plasma/serum & urine
zinc - serum & urine
Essential
elements / toxicity only: chromium – blood,
plasma & urine
cobalt - urine
iron – urine
manganese – blood & urine
Non-essential
elements: aluminium - plasma, urine, water &
dialysis fluid
arsenic - blood & urine
barium - serum & urine
cadmium - blood & urine
lead - blood & urine
lithium
- urine (occupational exposure only)
mercury
- blood & urine
nickel - urine
thallium - blood & urine
Multi-element screening of blood and urine and the investigation of individual, less commonly encountered, non-essential elements is possible using ICP-MS.
Complementary
analytes:
erythrocyte zinc protoporphyrin (ZPP) - blood
creatinine - urine
In
appropriate circumstances, analysis of other matrices such as tablets, powders
and liquid preparations will be attempted, but only following prior
consultation.
The laboratory aims to provide a turn-around-time of within 3 working days for serum copper, zinc and selenium and not greater than 10 working days for other analytes. IF APPROPRIATE CLINICALLY, urgent requests can usually be handled, but with prior consultation only. Printed reports can be faxed in advance of the hard copy.
Consultation is available on the validity, feasibility and design of large-scale projects e.g. clinical research studies and environmental investigations. Analyses will be undertaken if appropriate.
Using the Service
The service is open to clinicians and pathologists working in the NHS, Public Health and Private Health Care sectors and to those medical officers responsible for monitoring occupational exposure.
It is most important that appropriate specimens are collected for a particular investigation and that the containers used are contamination-free. Advice on these points is given below and in the SAS Trace Elements Handbook. If in doubt, please phone this laboratory.
For most analytical requests, prior arrangement with the laboratory is not necessary. However, please note that while a comprehensive nutritional investigation (e.g. serum copper, selenium and zinc) on one individual may be valid, the concept of a 'heavy metal screen' is more complex. Situations prompting this line of enquiry, or those involving ‘unusual’ metals (e.g. barium, thallium, uranium), should be discussed, in advance, with this laboratory so as to enable a sensible analytical approach to the problem to be followed. Similarly, specimens originating from projects such as clinical studies and environmental investigations will not be processed without appropriate prior discussion.
Specimens should be fully documented with respect to the following:
Source details (hospital, surgery, firm) and first-line contact
Personal details of individual being investigated including home post code
Time and date of collection
Reason for investigation
Details of diet or nutritional impairment or therapy
Details of treatment (e.g. chelation therapy)
Nature and duration of exposure to relevant trace element
Specimens,
securely boxed, should be dispatched to the laboratory by 1st Class Post or
Hospital Transport*. Specimens that need to be kept overnight or over a
week-end should be stored at 4oC and not frozen.
*New
packaging regulations came into force in January 2007, based on the UN-ECE
ADR2007, (http://www.unece.org/trans/danger/publi/adr/adr_e.html
The
packing instructions are detailed in: http://www.hse.gov.uk/biosafety/biologagents.pdf,
Contact Points
Mr. T.M.T. Sheehan. Principal Clinical Scientist & SAS Director: 0121 507 6028
Mrs. Aleha Khan Senior Clinical Scientist: 0121 507 4136 / 4137
Charges
All analyses, are
chargeable on a per test basis irrespective of origin.
Payment for NHS requests is the responsibility of the designated
budget-holder within the District, Trust or Fund-holding General Practice.
Unless
work is carried out as part of an agreed contract, invoices are issued
retrospectively at the end of each month. Each request for analysis must be
accompanied by full details of the
individual responsible for receiving statements and invoices; for new users of
the service, this must include written agreement to this responsibility.
Third party instructions to
invoice the company or patient directly are not acceptable.
Details
of the current charges for individual assays will be found in the separate
document "Charges for Laboratory Services".
Specimen collection and containers
Contamination is a major consideration in trace elements analysis and may arise from both the collection procedure and the container itself. Good hygiene should be practiced when collecting specimens, especially at 'dirty' sites such as factories. In the clinical setting, the situation may be more subtle: zinc and aluminium contamination has arisen from the powder used as lubricant in disposable gloves. Containers can be problematic and, whenever possible, products marketed for trace element analysis should be used (see Appendix 1). Glass must not be used for specimens for aluminium measurement. With respect to blood collection, zinc can be released by gel- separation systems, rubber stoppers and O-rings and be present in anti-coagulants. Lead can be released from rubber septa and cadmium from orange stoppers. 'Secondary' tubes, used for the storage and transportation of separated plasma or serum, must also be contamination-free. 24 hour urine collections should be made into containers that have been acid washed (1 mol/L HNO3, followed by ultra pure water rinse); ideally, urine for mercury measurement should be collected into (hard) polycarbonate containers to avoid loss by diffusion. Plastic 'Universal' containers (not those with metal caps and/or rubber cap-liners) are suitable for aliquots of 24 hour collections and for 'spot' urine specimens. They do not require acid-washing.
Preservatives such as boric acid
and thiomersal must not be used.
Specific requirements are discussed in the notes on individual trace elements. Note that, with the exception of investigations for Wilson’ Disease, a ‘spot’ urine is satisfactory most of the time. It is the urine option of choice for out-patient investigation and for occupational monitoring, when it should be collected at end of shift towards the end of the working week. For individuals hospitalised for the investigation and treatment of metals poisoning an aliquot of a 24 hour collection is preferred
Specimen volume requirements
The volume of blood normally collected (3 – 7 mL) is more than enough for the investigations listed below and can permit a single specimen to be used for more than one analyte e.g. blood lead and cadmium, or serum copper, zinc and selenium. When sampling from young children, and adults who are difficult to bleed, 2 mL (or smaller) paediatric collection tubes should be used. Analysis of specimens of very small volume will usually be attempted; however, there is usually little scope for mishap, for checking an anomalous result or for the performance of multi-element measurement. Such a minimum volume is listed for each element and matrix.
In the event of poisoning or exposure in which metals may be implicated, the following combination of specimens should be obtained: 5 mL whole blood (K-EDTA), 10 mL serum and 30 mL urine. Avoid glass containers and serum gel-separation tubes!
NOTES ON INDIVIDUAL TRACE ELEMENTS
The Essential Elements
Copper (Cu) - plasma/serum
Indications - Deficiency, hepato-biliary dysfunction
(inc. Wilson's Disease), toxicity.
Specimen requirements - 5 mL serum /plasma (minimum 50
µL).
Comment – (1) Raised values are seen in inflammatory states
and with steroid hormone therapy. (2) When investigating Wilson’s Disease,
plasma/serum Cu measurement is only of value as an addition to plasma
caeruloplasmin concentration and 24 hour urinary Cu excretion.
Reference
values:
Neonates – 4 months 0.1 - 0.7 mg/L 1.6 – 11 μmol/L
4 – 6 months 0.3 – 1.1 mg/L 4.7 – 17 μmol/L
7 – 12 months 0.5 – 1.3 mg/L 7.9 – 21 μmol/L
Children >12 months & adults: 0.7 - 1.6 mg/L 11 – 25 μmol/L
Pregnancy > 15/40: 1.6 - 2.5 mg/L 25 – 40 μmol/L
In healthy, premature infants, changes in serum copper concentrations appear to be related to subsequent growth rate.
Copper (Cu) - urine
Indications - Hepato-biliary dysfunction (inc.
Wilson's Disease), toxicity, occupational exposure.
Specimen requirements - 20 mL aliquot of 24 hour specimen collected into an acid-washed container. Spot urine acceptable for investigating acute toxicity and occupational exposure. Note that a ‘spot’ urine is not suitable for Wilson’s Disease investigations as the results are not easily interpreted.
Comment – (1) To distinguish Wilson's Disease from other forms of hepatic dysfunction, may require measurement of 24 hour urinary Cu excretion before and after penicillamine challenge. Consult this laboratory or the SAS Trace Elements Handbook. (2) Cu IUDs do not appear to increase excretion of or urine content of the element.
Reference values: (pre-chelation) amounts per 24 hours
Normal excretion usually < 50 µg / 0.8 μmol
Patients with cholestasis, hepatic cirrhosis,covert Wilson's Disease > 50 µg / 0.8 μmol
Patients with frank Wilson's Disease, acute hepatic crisis >100 ug / 1.6 μmol
Selenium (Se) - plasma/serum
Indications - deficiency, toxicity
Specimen requirements - 5 mL plasma/serum (minimum 50
µL). Separate without delay to prevent haemolysis.
Comment - plasma/serum Se is a good index of recent (months) changes in intake of or exposure to the element. However it is an acute-phase reactant and concomitant measurement of C-reactive protein may be useful in some circumstances as an aid to interpreting low Se concentrations.
Reference
values:
<18 months: 30 - 50 µg/L 0.38 – 0.63 μmol/L
18 months - 4 years: 45 - 90 µg/L 0.57 – 1.14 μmol/L
5 - 16 years: 55 - 115 µg/L 0.70 – 1.46 μmol/L
Adults (>16 years): 70 - 130 µg/L 0.89 – 1.65 μmol/L
Selenium (Se) - urine
Indications - toxicity, occupational monitoring.
Specimen requirements - 20 mL
urine.
Comment - Of no value in investigating deficiency.
Reference values: < 30 µg/g creatinine < 43 μmol / mol creatinine
< 50 µg/24 hrs < 0.63 μmol/24 hrs
Zinc (Zn) - serum
Indications - deficiency
Specimen requirements - 5 mL serum (minimum volume: 100
µL).
Comments - A relatively crude index of zinc status. May exhibit diurnal variation in 'healthy' individuals and is affected by number of factors including acute phase reaction, certain drugs and pregnancy. Concomitant measurement of C-reactive protein may be useful in some circumstances as an aid to interpreting low Zn concentration.
Reference values:
< 0.5 mg/L < 7.7 μmol/L May indicate zinc deficiency
0.5 - 0.7 mg/L 7.7 – 10.7μmol/L May have no clinical significance
0.7 - 1.6 mg/L 10.7 – 24.5 μmol/L 'Normal' range for all ages
> 1.6 mg/L > 24.5 μmol/L ? Dietary supplement use (or contamination)
Zinc (Zn) - urine
Indications - metabolic studies, chelation therapy,
occupational exposure to zinc fume.
Specimen requirements - 20 mL aliquot of 24 hour
collection; spot urine for occupational monitoring.
Comments - Of little value in assessing
deficiency. May be of value in monitoring the effect on zinc body burden of
extended chelation therapy for the removal of other metals.
Reference values:
Excretion usually:
200 - 1400
mg/24
hrs 3 – 21 μmol/24 hrs
Essential Elements – investigations for toxicity or exposure only
Chromium (Cr) – blood, plasma & urine
Indications – toxicity (including PN overload),
occupational exposure.
Specimen requirements - 5mL blood; EDTA (minimum
volume: 100 µL); 20 mL urine. For occupational monitoring, collect urine at
end of working week.
Comments - (1). In acute poisoning, measurement of Cr in whole blood and urine is the approach of choice. Plasma and erythrocyte concentrations can yield information as to form of the element involved. (2) For suspected PN overload, plasma measurement is used.(3). For on-going occupational exposure, urine is the preferred specimen. In cases where exposure has ceased, or has occurred sporadically, within the last four weeks, blood measurement is more useful. In all circumstances particular care is needed to avoid contamination when collecting specimens. (4). Monitoring for Cr ‘deficiency’ is not undertaken because (a) the problem has yet to be convincingly demonstrated in humans and (b) it is extremely difficult to collect blood without contaminating it to concentrations within the normal range. (5) Concentrations in blood, plasma and urine may be elevated in individuals with metallic prosthetic joints, but the significance of this phenomenon is unclear as yet.
Reference values:
Blood: < 2 µg/L < 40 nmol/L
Serum/plasma: < 0. 5 µg/L < 10 nmol/L
Urine: < 1 µg/g creatinine < 2 μmol/mol creatinine
Cobalt (Co) – urine
Indications – occupational exposure.
Specimen requirements – 20 mL urine collected end of
shift, towards the end of the working week.
Comments: (1) Only known essential role is as component of Vitamin B12. Investigation of ‘cobalt deficiency’ per se is, therefore, inappropriate and would, in any event, be technically extremely difficult. (2) Analysis of blood & plasma is available, but application is limited apart from wrt individuals with metallic prosthetic joints. Cobalt values can be markedly raised in some such patients, but the significance of this is unclear, apart from, perhaps, indicating degree of joint degradation.
Reference values:
Urine:
1
µg/g creatinine < 2 μmol/mol creatinine
Iron (Fe) – urine
Indications
– iron
overload; monitoring chelation therapy
Specimen
requirements:
20 mL aliquot of a 24 hour collection.
Comments
–Primarily for investigations relating to haemochromatosis or transfusional
siderosis.
Reference values:
Excretion usually:
<
50
µg / 24 hours < 0.9
μmol / 24 hours
Manganese (Mn) – blood & urine
Indications – toxicity (particularly PN overload)
Specimen requirements: 5 mL blood (EDTA – minimum volume 100 µL);
20 mL urine.
Comments – (1). Blood measurement is the approach of choice for investigating PN overload. (2) For other situations, blood and urine should be sent, although the usefulness of analysis for occupational monitoring purposes is questionable unless the exposure has been gross. (3) Monitoring for Mn ‘deficiency’ is not undertaken because (a) the problem has yet to be convincingly demonstrated in humans and (b) it is extremely difficult to collect blood without contaminating it to concentrations within the normal range.
Reference values:
Blood: children < 1 year: 7 – 18 µg/L 120 – 335 nmol/L
children > 1 year, adults: 4 – 12 µg/L 73 – 210 nmol/L
risk of toxicty: > 20 µg/L > 360 nmol/L
Urine: < 1µg / g creatinine < 2 μmol/mol creatinine
The Non-essential Elements
Aluminium (Al) - plasma
Indications - chronic renal failure, occupational
exposure, gross environmental
exposure.
Specimen requirements - 5 mL plasma. (Minimum volume 50
µL) Special Al-free tubes must
be used! Send specimens to this laboratory unseparated.
Comments - The service is primarily for monitoring situations in which patients with renal impairment may be exposed to excessive amounts of Al by virtue of their treatment, i.e. chiefly those with chronic renal failure, but also premature infants on long-term parenteral feeding. For individuals with normal renal function, in most cases, this measurement is of little value as plasma Al concentrations are an index of very recent exposure only (days) and give no information on body burden. Exceptions to this may be occupational and gross environmental exposure. In these circumstances the laboratory must be contacted before specimens are taken.
Reference values: (Commission of the European Community [CEC] Recommendations for patients receiving dialysis)
< 10 µg/L < 0.37 μmol/L Normal (no history of CRF)
< 60 µg/L < 2.22 μmol/L Desirable in CRF patients
> 60 µg/L > 2.22 μmol/L Excessive accumulation
> 100 µg/L > 3.70 μmol/L Cause for concern; high risk of toxicity in children
> 200 µg/L >7.41 μmol/L Urgent action required: high risk of toxicity in all
Aluminium (Al) - water
Indications - Treatment of chronic renal failure by
dialysis
Specimen requirements - 2 x 10 mL per sampling point.
Special Al-free tubes must be used! These are available from this
laboratory.
Comments - This service is primarily for
monitoring the Al content of water used in renal dialysis systems. Duplicate
aliquots are taken from the mains supply and from the outlet of any water
purifier used in the system. Requests for analysis of water obtained in other
circumstances are likely to be inappropriate unless extensive precautions are
taken to avoid contamination with respect to both container and sampling.
Reference
values: (CEC Recommendations)
Maximum allowable concentration (MAC) for potable water:
200 µg/L
Guide Line Concentration (GLC) for potable water:
50 µg/L
MAC for water for preparation of dialysis fluid:
30 µg/L
Aluminium (Al) - dialysis fluid
Indications - Treatment of chronic renal failure by
dialysis
Specimen requirements - 2 x 10 mL. Special Al-free tubes must be used! These are available from this
laboratory.
Comments - If Al content is unacceptable, both
concentrate and water used for dilution should be investigated.
Reference
values: (CEC Recommendation)
MAC for dialysis fluid:
30 µg/L
Aluminium (Al) - urine
Indications - Occupational exposure, gross
environmental exposure.
Specimen requirements - 20 mL spot urine. Special
Al-free containers must be used. These are available from this laboratory.
Comments - Gives a slightly broader window of
exposure (weeks) than plasma Al, but again provides no useful data on body
burden. Useful as indicated above, but laboratory should be contacted before
specimens are taken.
Reference values:
< 25 μg/g creatinine < 105 μmol/mol creatinine
< 25 µg/24 hrs < 0.9 μmol / 24 hours
Arsenic (As) – blood & urine
Indications – toxicity, occupational exposure.
Specimen requirements- 5 mL whole blood (EDTA) (minimum
volume: 100 µL). 20 mL urine. For occupational monitoring collect specimen at
end of working week.
Comments – (1). For acute poisoning both blood
and urine should be sent. (2) For suspected chronic exposure and for
occupational monitoring, urine is the specimen of choice in the first
instance. (3) It is important to know, if available, the nature and duration
of exposure as a sea food diet can produce considerable quantities of
detectable As and all forms of the element are excreted rapidly (48 hours).
(4). Analysis is made for total non-dietary arsenic.
Reference values:
Blood (Inorganic As + metabolites): < 10 µg/L < 0.13 μmol/L
Urine (Inorganic As + metabolites): < 10 µg/g creatinine < 15 μmol/mol creatinine
Barium (Ba) - serum & urine
Indications - acute & chronic poisoning;
occupational exposure.
Specimen requirements - 5 mL serum (minimum volume 100
µL); 20 mL urine.
Reference values:
Serum: < 1 µg/L < 7 nmol/L
Urine: < 5 µg/g creatinine < 4 μmol/mol creatinine
< 5 μg/24 hours < 35 nmol/24 hours
Cadmium (Cd) - blood & urine
Indications - occupational exposure, environmental
exposure, acute & chronic poisoning
Specimen requirements - 5 mL whole blood; EDTA.
(Minimum volume 100µL); 20 mL urine.
Comments - (1). Blood is the first-choice matrix.
Urine Cd is not normally measured unless blood Cd is elevated. (2). Smokers
tend to have raised Cd concentrations.
Reference values:
Blood: Non-smoker: < 1 µg/L < 10 nmol/L
Smoker: < 3 µg/L < 30 nmol/L
Significant exposure: > 10 μg/L > 90 nmol/L
Urine: < 2 µg/g creatinine < 2 μmol/mol creatinine
Lead (Pb) - blood
Indications - acute & chronic poisoning from,
occupational and environmental exposure to inorganic
Pb.
Specimen requirements - 5mL whole blood; EDTA (minimum
volume: 50µl).
Comments - blood Pb is the best index of exposure
in these circumstances. ZPP and Hb measurements may give useful complementary
information.
Reference values:
Children & non-occupationally exposed adults: < 10 µg/dL < 0.48 μmol/L
Current threshold for paediatric follow-up: 10 µg/dL 0.48 μmol/L
Occupational suspension levels*:
Females (child-bearing age): 30 µg/dL 1.4 μmol/L
Males (16 – 18 years): 50 µg/dL 2.4 μmol/L
All other workers: 60 µg/dL 2.9 μmol/L
*Control of Lead at Work. Approved code of Practice HMSO,1998
Lead (Pb) - urine
Indications- Occupational exposure to organic
Pb; monitoring chelation therapy.
Specimen requirements - 20 mL spot urine (occupational
exposure); aliquot of 24 hour specimen for chelation assessment.
Comments - The metabolism and distribution of organic Pb differ markedly from the inorganic form and urine is the matrix of choice for investigating exposure. It is of no value in monitoring exposure to inorganic Pb except when chelation therapy following poisoning is being assessed.
Reference values:
Non-occupationally exposed individuals: < 10 µg/g creatinine < 5 μmol/mol creatinine
< 10 µg/24 hours < 48 nmol/24 hours
Occupational suspension levels*:
Females (child-bearing age): 25 µg/g creatinine 14 μmol/mol creatinine
All other workers: 110 µg/g creatinine 60 μmol/mol creatinine
* Control of Lead at Work. Approved code of Practice (HMSO, 1998)
Lithium (Li) - urine
Indications - occupational exposure.
Specimen requirements - 20 mL spot urine.
Comments - this service is for occupational
monitoring only. This laboratory does not provide a therapeutic monitoring
service for Li therapy.
Reference values: < 50 µg/g creatinine < 0.8 μmol/mol creatinine
Mercury (Hg) - blood
Indications - exposure to organic Hg compounds;
serious, acute exposure to vapour or inorganic salts.
Specimen requirements - 10 mL whole blood. (EDTA or Li
Heparin)
Comments - For investigation of chronic exposure
of to vapour or inorganic salts, urine is the matrix of choice.
Reference
values:
<
4 µg/L < 20 nmol/L
Mercury (Hg) - urine
Indications- exposure to elemental Hg or to
inorganic Hg salts.
Specimen requirements - 20 mL urine. Freeze aliquot if
same day dispatch is not possible.
Comments - analysis of specimens from individuals
concerned about the leaching of Hg from dental fillings has not to date proved
useful.
Reference values:
< 10 µg/g creatinine < 5 μmol/mol creatinine
< 10 µg/24 hrs < 50 nmol/24 hrs
Nickel
(Ni) – urine
Indication – occupational exposure, toxicity
Specimen requirements – 20 mL urine.
Comments – not appropriate for confirming
sensitivity to nickel-containing jewellery.
Reference values: < 5 µg/g creatinine < 5 μmol/mol creatinine
< 5 μg/24 hr < 85 nmol/24 hr
Thallium (Tl) - blood & urine
Indications - acute & chronic poisoning;
occupational exposure.
Specimen requirements - 5 mL whole blood; EDTA. 20 mL
urine.
Reference values:
Blood: < 1 µg/L < 5 nmol/L
Urine: < 1 µg /g creatinine < 0.5 μmol/mol creatinine
< 1 μg/24 hr < 5 nmol/24 hr
Complementary Analytes
Erythrocyte zinc protoporphyrin (ZPP) - whole blood
Indications - Pb poisoning; occupational exposure to Pb.
Specimen requirements - 5 mL whole blood (EDTA); that taken for Pb analysis is used.
Comments - [ZPP] rises, and returns to baseline more slowly than [Pb]; it can help differentiate acute from chronic exposure and aid estimates of the period of the latter. N.B. It is also elevated by iron deficiency anaemia.
Reference range:
In 'non-exposed' individuals, i.e. those with blood [Pb] < 10 µg/dL (0.48 μmol/L )where iron-deficiency anaemia is absent, whole blood [ZPP] is usually < 3.5 µg/g haemoglobin. Note, however, that, neonatal values may be three-fold higher, declining to adult concentrations over the first year of life.
For occupationally exposed individuals, [ZPP] must not exceed 20 µg/g haemoglobin, although this stipulation is secondary to blood [Pb] and such a value is most likely to be achieved with [Pb] > 60 µg/dL (2.9 μmol/L).
