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Pathology Handbook

Pathology User Handbook

Section 2: Department of Clinical Biochemistry

Table of Contents

2.1 Departmental telephone numbers

For non-clinical matters please call:

Richard Headford

Laboratory Manager

01225 824714

Amanda Speed

Chief Biomedical Scientist

01225 824712

Richard Morgan

Chief Biomedical Scientist

01225 824709

For clinical matters, please call:

Dr Andrew Taylor

Consultant Medical Biochemist

01225 824715

Frances Eggbeer / Sam Elwin

Secretary

01225 824710

Miss Jane Lewis

Consultant Clinical Scientist

01225 824711

Miss Beverley Harris

Principal Clinical Scientist

01225 824713

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2.2  Aims of Biochemistry

The Department aims to provide clinical users with a comprehensive service for biochemical tests which meets their needs for diagnosis and monitoring of conditions with a biochemical component.  This involves provision of appropriate analytical tests of a high technical quality and with a satisfactory turnaround time, and provision of an interpretative service for these test results when required. Advice may be obtained on the selection of tests, planning of investigations, interpretation of results and therapeutic intervention, as appropriate.

Although almost all biochemical results are numerical, users should be aware that a large number of factors may influence these numbers in addition to the illness for which the patient is being investigated: such factors include age and sex, sampling times, diet and medication, biological (within-patient) variability, delay in analysis, and analytical variability and interferences from drugs and diet. We aim to provide advice on these matters, and in order to help us provide interpretation of results, relevant clinical details should be included on the request form, the most important of which is the reason why the test is being requested, i.e. what question needs to be answered?

Demands on the Department naturally change with time - new tests may be introduced and others replaced - we aim to discuss potential developments with users. Similarly, we would wish to be involved in any plans to introduce new Point of Care Testing facilities; this is obligatory under the Guidelines of the National Joint Working Group on Quality Assurance.

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2.3  Laboratory Hours

Please refer to the Table in Section 1.2 for Opening Hours.  For further information please contact the Laboratory Manager.

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2.4  Urgent Requests During Core Hours

With the exception of Acute Wards the Biochemistry Department needs prior notification to process requests urgently.  If you require an urgent analysis please telephone the Laboratory Specimen Reception on 01225 824740.

The laboratory may need to discuss with you the validity of the urgent test; the running of tests is prioritised according to need, therefore turn around times for urgent samples may be increased when the pressure of work is high, this is particularly applicable during the early evening; please indicate on the request form or ICE request how you may be contacted. Abnormal results of urgent requests will be telephoned to the Ward or GP Practice and made available on Ultraconnect and ICE.

To add tests to existing requests please leave details on answerphone on 01225 821658.

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2.5  Requests Received Outside Core Hours

Urgent requests from Acute Wards will be automatically be fast tracked outside Core Hours.  Urgent requests from other sources will be fast tracked if they are clearly labelled as URGENT.  If there is an unusual requirement this should be discussed with the BMS on duty, who may refer the request to a laboratory clinician.

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2.6 How to Request Investigations

Requests must be made using ICE or an RUH request form.  The Department will not be held responsible for any consequences, including costs, arising from samples which have been sent to other laboratories without our involvement.

To request additional tests to previously received samples, please use the icemail additional test service or call the, voicemail add-on service on ext 1658 and follow the recorded instructions. For urgently required extra tests please send a fresh sample.

Please note: samples are only kept for ~4 days and it is therefore impossible to add extra tests to samples greater than 4 days old. In addition to this restriction, it may not be appropriate to add certain investigations to previously received samples, if in doubt please contact the laboratory, or send a fresh sample.

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2.7  Sample Collection

2.7.1  Blood Samples

Full details of the type of sample container required, special notes about collection, reference ranges and target turnaround times are listed on the blood test A - Z.  Information on some problematic tests is given below.

The majority of estimations on blood are carried out using  a sample taken into a Becton Dickinson Vacutainer SST tube which contains 1/2 inch of gel in the bottom and has a yellow stopper.   A clotted sample is produced, the serum from which is then analysed. Some tests require the sample to be taken into a different tube: the common ones are given below, but for unusual tests it is wise to consult the Index of Tests at the end of this Section, or the pathology pages of the Trust website, or by contacting  the Department, prior to collecting the samples.

Specimens for Glucose should be collected into a Fluoride/oxalate tube (grey top). Please contact the laboratory if testing from an SST sample is required.

To ensure high quality samples, e.g. no haemolysis, ideally blood should not be collected using a syringe and needle. If it is, it should be transferred to the Vacutainer tube(s) using a special transfer device. Vacutainer tubes that have had their stoppers removed and replaced, to enable it to be filled should be sent by hand and must not be sent by the pneumatic air tube, as they will be prone to leaking. It is not possible to provide valid results for many tests on samples which are haemolysed.

Blood gases require the sample to be taken into a heparinised syringe: this should be kept in iced water and transported to the laboratory with minimum delay (sample is only stable for 30mins).  Please ensure that a safety cap is fixed firmly over the luer of the syringe. Samples will not be accepted if received with needles still attached as these present a significant risk of needlestick injury.   Please ensure a request  form is sent with the blood gas samples and that it is kept dry by placing it in the zip-lock section of the specimen bag with the sample.

Paediatric Samples
Special paediatric tubes are available for very small samples.  Paediatric Bilirubins should be collected into a clotted or heparinised paediatric tube and kept in the dark before analysis.

Haemoglobin  A1c, Lead, blood Porphyrins and Cyclosporin estimations
Require an EDTA tube (purple top). 

Trace metal estimations
Eequire special tubes - please contact the laboratory.

Some assays are only available by special request.
Please contact the Biochemistry Department before collecting the sample.   Whoever takes these blood samples is responsible for ensuring they are delivered to the pathology dept within the required time frame.    Please warn the laboratory (01225 824740) that these samples are coming and need to be processed quickly.

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2.7.2  Urine Samples

Full details of the type of sample container required, preservatives, special notes about collection, reference ranges and turnaround times are listed alphabetically at the end of this chapter - general advice and discussion of more problematic tests  is given below.

Most samples can be taken into a plain container, either a 20 ml Universal or a 24hr container, depending on collection period required. Important exceptions are 5HIAA and Catecholamines (VMA, Metadrenaline), which must be collected into special 24hr bottles, containing acid preservative.

24 hour containers – with no preservative are available for the following tests, on a named-patient basis.  Please contact laboratory to order container:
Calcium & Phosphate
Creatinine clearance
Electrolytes & urea
Urine free cortisol
Protein
Urate

20ml Universal containers (white-top) – no preservative - should be used for the following tests:
Random urea & electrolytes
Osmolality
Porphyrins (a fresh sample kept shielded from light is essential)
Bence-Jones Protein (Early Morning Urine) (Please also send blood for electrophoresis)
Metabolic screens (fresh) (Please include full clinical details)

10 ml Urine tubes
Microalbuminuria - albumin:creatinine ratio on an early morning urine (starting Jan 2011)

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2.7.3  Pleural Fluid Samples

When requesting biochemistry tests on pleural fluids, the request form should be labelled as "Low Risk" if there is no evidence of Tuberculosis empyema or HIV infection. If the form is not labelled "Low Risk" , the sample will not be processed.  Samples for pH analysis must be aspirated into a heparinised blood gas syringe, capped, labelled before transportation to the laboratory on ice.

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2.7.4  Other Samples

Samples of faeces, cerebrospinal, pleural, ascitic and drain fluids may be analysed by the laboratory. As some of these fluids may be difficult to analyse on the automatic analysers; discussion with the laboratory prior to sending the samples to the lab, is recommended.

Full details of the type of sample container required, special notes about collection, reference ranges are listed on the blood test A - Z.

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2.8  Patient Preparation

In general venous stasis should be minimised, as this causes artefactual increases in plasma proteins and their associated analytes (important ones are lipids and calcium). It may be necessary to take the sample without a tourniquet.

Recumbence is relevant to renin and aldosterone determination.

Although cholesterol may be determined on a random sample, triglycerides and HDL-cholesterol require a fasting period of 10-12 hrs before taking the sample.

Drug and dietary restrictions may apply to some tests (notably renin & aldosterone), and for unusual ones it is recommended that advice is sought from the laboratory, prior to sampling.

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2.9  Test Groups or Profiles

Certain tests fall naturally into organ- or disease- related groups, and these may be requested as a test group. Examples are shown below.

C & E

Creatinine and Electrolytes (Sodium & Potassium). 
(Urea is not measured as standard and  must be specifically requested if required)

Calcium Group

Calcium, Phosphate, Albumin, Alkaline hosphatase, Corrected Calcium (calculated where the albumin is 41g/L or less)

LFTs

Total Bilirubin, Total Protein, Albumin, Alkaline Phosphatase, Alanine Transaminase, Globulin (calculated)

Fasting Lipid

Cholesterol, Triglyceride, HDL cholesterol (a fasting sample is required)

Thyroid Function

TSH is the front-line test.  Free T4 and Free T3 will be measured as appropriate.  Clinical details / therapy required

Cardiac Enzymes

Creatine kinase – post onset timed serial samples required. Troponin – sample timings must follow cardiac protocol.

All other tests must be requested individually.

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2.10  Paediatric Service

Routine Biochemistry

For neonates and young children, a minimum of 100 μl plasma (paediatric Lithium-Heparin sample tube) is required for C&E;  if additional tests are needed, e.g. bone profile or LFT, up to 500 total plasma volume may be required depending on the number and type of analytes requested.  Depending on haematocrit, at least twice as much whole blood is required for these plasma yields.   If it is not possible to take a sample of sufficient volume, please indicate the priority of the tests requested.

For older children, please collect blood into 6 ml SST tube as usual for adults.

Investigation of Possible Inborn Error of Metabolism

Some basic screening tests are available on site (lactate, ammonia, mucopolysaccharides, reducing substances, ketones, porphyrins) but additional important investigations to exclude or identify an inherited metabolic disorder (organic and amino acids), and specialised or confirmatory tests (e.g. very long chain fatty acids, white cell enzymes), require samples to be sent to Bristol (Southmead or UHB) and occasionally other specialist departments. The laboratory will arrange transport and liaise with these external laboratories for you.

Many assays have special sample requirements and the Duty Clinical Staff (01225 824713) should be contacted before collection.  It is imperative that full clinical information (see below) is given to enable results to be interpreted and further analyses instigated by the laboratory at the time if necessary.  Samples are usually transported to the Bristol hospitals on Monday, Wednesday and Friday, leaving the laboratory at 12.30. 

Where presentation is an acute life-threatening event, it is important to inform the laboratory of the urgency of the investigations so that the receiving laboratory may be contacted and special transport arranged if necessary.  If possible, samples (blood and urine) should always be taken during an acute attack, and before commencing any therapy, in order that they may be stored for later analysis for Inborn Errors of Metabolism if necessary.  Where presentation is "non-urgent", planned investigation is important as specialist laboratories may need to be consulted before samples are taken.

A Urine Metabolic Screen consists of analysis of amino acids and an organic acid profile by GC/MS. Additional analyses (e.g. reducing substances,  ketones) must be specifically requested where required. Samples must be fresh (random, plain bottle); in the event of delay in despatch to the laboratory, store frozen.  The majority of amino acid and organic acid disorders should be eliminated by these tests, providing the patient is suitably stressed and receiving adequate protein intake.  If there is a high index of clinical suspicion, and screening results are normal, please contact the laboratory to discuss further investigations.  Note that a few disorders can rarely or never be identified by urine testing and these will not have been eliminated by a 'normal' profile. 

Requests for screening should include any relevant presentation details i.e. abnormal smell, cataracts, neurological dysfunction/degeneration, hepatosplenomegaly, cardiomyopathy, failure to thrive (persistent vomiting, poor feeding, developmental delay), dysmorphic features and any evidence of unexplained hypoglycaemia, acid-base imbalance or liver dysfunction.  Preliminary biochemical investigations would be expected as follows: blood gases, electrolytes, creatinine, glucose, calcium, magnesium, bilirubin, alkaline phosphatase, alanine transaminase.  Information regarding feeding regime and medication should also be included.

For sample details, please see Sections on Blood and Urine Tests.

For further information, contact Jane Lewis, Consultant Clinical Scientist on 01225 82 4711 or Beverley Harris, Principal Clinical Scientist on 01225 824713

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2.11  Guidelines for Requesting Tests

The laboratory offers a wide repertoire of tests, many of which can be reported very quickly when this is needed; even tests that normally have a long turnaround time can be expedited if there is an overriding clinical need, but this needs to be discussed with laboratory clinical staff. However, providing such results urgently interferes with the processing of other tests and should be kept to a minimum to help other users. This is particularly true during the period outside the weekday Core Hours of 08.00 – 17.15.

The service operating outside the weekday Core Hours  is provided by a small number of staff providing  single-handed service to cover all urgent and some routine workload. In order to reduce unnecessary requests made during these times, guidelines were agreed with the Division of Medicine on the appropriate availability of certain tests. Tests which are generally available are shown below; some are restricted for use only in the investigation of patients with certain conditions; in exceptional circumstances it may be appropriate to do tests not covered below, but this will need to be discussed with the laboratory clinical staff first, particularly if the result is required urgently.

Tests offered Urgently:-

(This is not an exhaustive list. Please contact the laboratory for any queries.)

Prior discussion required, potentially available in management of overdose/intoxication:

Prior discussion required, potentially available in management of asthma/COAD:

Prior discussion required, potentially available in investigation of inborn error of metabolism:

Please note that tests requested because of suspected occupational exposure to toxins (e.g. Cadmium, Lead) are not covered by NHS service. These are Category II tests: a fee to the laboratory is mandatory.

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2.12  Dynamic Function Tests

Protocols for several Dynamic Function Tests are available from the laboratory; these are listed below. Advice on more unusual tests may also be available: please contact the laboratory. If you are unsure about the indications for these tests, testing strategy for the investigation of a disorder or practicalities of a test procedure, please contact the laboratory.

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2.13  Reference Ranges, Special Notes, Turnaround Times for each Test

Reference ranges change as methodology change please refer to the RUH web site for up to date reference ranges.   


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