GUIDE TO TRACE ELEMENTS MONITORING SERVICE

Copyright © [Regional Laboratory for Toxicology], 2005. All rights reserved.

Introduction

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. A.W. Walker. 3rd Edition, Guildford 1998) 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 members of the U.K. SAS and Associated Trace Element Laboratories.

Analysis is performed by atomic absorption spectrometry (flame and electro-thermal) and inductively coupled plasma mass spectrometry (ICP-MS). 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 not greater than 10 working days for most analytes, batches for the frequently requested elements being run as follows: serum copper, zinc and selenium - at least twice weekly; blood lead, plasma and water aluminium and urine copper - weekly. 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 July 2005, based on the UN-ECE ADR2005, http://www.unece.org/trans/danger/publi/adr/adr_e.html

within Packing Instruction P650. To comply with the new legal requirements, all packaging MUST be used and sealed correctly. The outer container of the triple package MUST bear the words “Diagnostic Specimen” or “Clinical Specimen” and also bear the UN 3373 diamond mark.

The packing instructions are detailed in: http://www.hse.gov.uk/biosafety/biologagents.pdf,

in appendix 1.2 (Transport of infectious substances) as Packing Instruction P650 on page 58. Please note that the 100mm minimum external dimension requirement has been deleted from P650:  http://www.unece.org/trans/danger/publi/adr/adr2005/ECE-TRANS-175-Corr1e.pdf

 

Contact Points

 Mr. T.M.T. Sheehan,                Principal Clinical Scientist

                                              & Deputy Head of Department: 0121 507 6028 / 4137

Dr. R.A. Braithwaite,                 Head of Department: 0121 507 4134/5

Miss Aleha Khatun,                   Section Team Leader:  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. 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 and summarised in Table 1. 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

Appendix 1 lists a number of companies that manufacture specimen containers specified as being suitable for trace element analysis or have been found to be suitable for that purpose by this laboratory. Please note that a charge may be made (equal to the cost of the analysis) if it is necessary to check the contamination status of an empty duplicate tube received in parallel with a specimen.

Specimen volume requirements

 The blood collection tubes listed Table 1 use volumes of 5 - 10 mL, the usual quantity under normal sampling circumstances. This is usually more than enough for analytical purposes 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 100 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:

          Term Neonates*:                       0.2 - 0.7 mg/L

          By 7 days*:                               0.3 – 1.1 mg/L

          Children > 6 mth* & adults:        0.7 - 1.6  mg/L

          Pregnancy > 15/40:                   1.6 - 2.5  mg/L

* Note that in healthy term neonates there is a gradual increase in values between one week and six months of age. This is a dynamic period and defining a ‘normal’ serum copper at any one instant is difficult. 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)

          Normal excretion usually                                                               < 50 µg/24 hrs

          Patients with cholestasis, hepatic cirrhosis,covert Wilson's Disease      > 50 µg/24 hrs

          Patients with frank Wilson's Disease, acute hepatic crisis                   >100 ug/24 hr  


 

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

18 months - 4 years:                                     45 - 90 µg/L

5 - 16 years:                                                 55 - 115 µg/L 

          Adults (>16 years):                                       70 - 130 µg/L

 

Selenium (Se) - urine

Indications - toxicity, occupational monitoring.

Specimen requirements - 20 mL  urine.

Comment - Of no value in investigating deficiency.

Reference values:

          Excretion usually:   < 30 µg/g creatinine / < 50 µg/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                               May indicate zinc deficiency

          0.5 - 0.7 mg/L                           May have no clinical significance

          0.7 - 1.6 mg/L                           'Normal' range for all ages

          > 1.6 mg/L                               ? Dietary supplement use.

 

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


 

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.

 

Reference range:

          Blood:                                      < 2.0 µg/L

          Serum/plasma:                          < 0. 5 µg/L

          Urine:                                       < 1.0  µg/g creatinine


 

Cobalt (Co) – urine

Indications – occupational exposure.

Specimen requirements – 20 mL urine collected end of shift, towards the end of the working week.

Comments:  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.

Reference range:

          Urine:                                < 1.0  µg/g 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 range:   

           Excretion usually:                      < 50 µg / 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 range:

          Blood:         children < 1 year:                      7 – 18 µg/L

                             children > 1 year, adults:           4 – 12 µg/L

                             risk of toxicty:                           > 20 µg/L

 

          Urine:                                                         < 1µg / g 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              Normal (no history of CRF)

          < 60 µg/L              Desirable in CRF patients

          > 60 µg/L              Excessive accumulation

          > 100 µg/L            Cause for concern; high risk of toxicity in children

          > 200 µg/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 range: (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 range:

             Excretion usually:                            < 25 µg/24 hrs


 

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 range:

          Blood:                                                         < 10 µg/L (Inorganic As & metabolites)

          Excretion (inorganic As & metabolites) usually: < 10 µg/g creatinine

                                                                            < 10 µg/24 hours


 

Barium (Ba) - serum & urine

Indications - acute & chronic poisoning; occupational exposure.

Specimen requirements - 5 mL serum (minimum volume 100 µL); 20 mL  urine.

Reference range:

          Serum:                                      < 1 µg/L

          Urine:                                       < 4 µg/24 hr


         

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 range:

          Blood:      Non-smoker:                                          < 3.0 µg/L

                         Smoker:                                                 < 6.0 µg/L

                         Acceptable occupational exposure:         <  10.0 µg/L

          Urine:       Non-smoker:                                          < 1.0 µg/g creatinine

                         Smoker:                                                 < 3.0 µg/g creatinine

                         Acceptable occupational exposure:         < 10.0 µg/g creatinine


         

Lead (Pb) - blood