COVID-19 information

Visiting is once again welcomed at The Walton Centre. So that we can safely reintroduce visiting, visits should be pre-booked with an allocated appointment slot.

General safety measures remain in place at The Walton Centre - and in our other clinic settings within the community – until further notice. 

Neurobiochemisty Diagnostic tests

Beta trace protein

Beta trace protein (BTP) 

Also known as 

Prostaglandin D2 synthase 

Assay Information 

Beta trace protein (BTP) is a low molecular weight protein (24kDa) also known as prostaglandin D2 synthase.  BTP is mainly synthesized in the central nervous system by glial cells and the choroid plexus and forms one of the principle constituents of cerebrospinal fluid (CSF).  BTP concentrations are therefore much higher in CSF than in serum or plasma so it is a useful marker for detecting CSF leakage in fluids such as nose or ear secretions.  In the Neuroscience Labs, BTP is used as a first line test for ?CSF fluids.  Beta-2-transferrin is reserved as a second line test for specimens that are unsuitable for BTP analysis, or those that give an equivocal BTP result.  

 

Virtually all circulating BTP is filtered by the kidneys therefore the plasma concentration is mainly dependent on the glomerular filtration rate.  Serum BTP can therefore also be used as a marker of renal function in some scenarios.  However the Neurosciences Laboratories do not use the assay for this purpose. 

 

BTP is analysed by nephelometry.  The reagent contains polystyrene particles coated with antibodies to human BTP.  When a sample containing BTP is added, the particles aggregate and scatter a beam of light passed through the sample.  The intensity of the scattered light is proportional to the concentration of BTP in the sample. 

 

Note - Beta Trace Protein (BTP) is the first-line screening test. Beta 2 transferrin (B2T) will be performed when sample is unsuitable for BTP e.g. small volume, too viscous, sample haemolysed etc. B2T will also be performed if BTP result is equivocal. 

 

Specimen Type(s) & Minimum Volume 

Fluid / secretion – 0.2 mL  

Note 1 – serum is useful to aid interpretation, but do not delay sending fluid if serum is not available. 

Note 2 – please centrifuge bloodstained or contaminated fluids as soon as possible and send supernatant. Please ring if further advice required. 

Cost 

 

£42.00 

 

Beta trace protein and/or beta 2 transferrin will be analysed depending on sample/results. Cost fixed regardless of assay(s) performed. 

 

Transport 

 

First class post 

 

Frequency of Analysis/Turnaround Time 

2 Working Days 

Assay Method 

Nephelometry  

 

Reference Range & Units 

<0.7 mg/L 

 

Factors Affecting Performance of Examination 

 

Renal insufficiency 

Patients with normal pressure hydrocephalus or meningitis. 

Over dilution with other bodily fluids. 

Blood stained samples 

Related Tests 

Beta-2 transferrin 

Note - Beta Trace Protein (BTP) is the first-line screening test. 

Accredited Assay 

 

UKAS 8642 

 

External Quality Assurance (EQA) 

UK NEQAS for CSF B2 Transferrin/Beta Trace Protein 

Further Information 

 

emailwcf-tr.neurobiochemistry@nhs.net 

 

Telephone: 0151 5563262 

 

References 

Bernasconi L, Pȍtzl T, Steuer C, et al. Retrospective validation of a β-trace protein interpretation algorithm for the diagnosis of cerebrospinal fluid leakage. Clin Chem Lab Med. 2017; 55(4): 554-560. 

Meco C, Oberascher G, Arrer E, Moser G and Albegger K. Beta-trace protein test: new guidelines for the reliable diagnosis of cerebrospinal fluid fistula. Otolaryngol Head Neck Surg. 2003; 129(5): 508-17. 

Kleine TO, Damm T, Althaus H. Quantification of beta-trace protein and detection of transferrin isoforms in mixtures of cerebral fluid and blood serum as models of rhinorrhea and ottorrhea diagnosis. Fresenius J Anal Chem. 2000; 366: 382-6. 

Date last updated 

Tuesday, 17 August 2021 

Beta-2-Transferrin

 

Beta-2 transferrin 

Also known as 

Asialo-transferrin 

Note – beta 2 transferrin is sometimes called Tau protein. This is not recommended to prevent confusion with the dementia marker. 

Assay Information 

The assay enables the detection of beta 2 transferrin (asialo-transferrin), to determine the presence of CSF in rhinorrhoea and otorrhoea fluids. 

 

The method separates transferrin and asialo-transferrin by electrophoresis on a high-resolution agarose gel, followed by transfer onto nitrocellulose membrane. Following blocking, the membrane is incubated with goat anti-human transferrin and then, following washing, with peroxidase-conjugated anti-goat IgG. The results are visualised by addition of a chromagen. 

 

Note - Beta Trace Protein (BTP) is the first-line screening test. Beta 2 transferrin (B2T) will be performed when sample is unsuitable for BTP e.g. small volume, too viscous, sample haemolysed etc. B2T will also be performed if BTP result is equivocal. 

 

Specimen Type(s) & Minimum Volume 

Fluid / secretion – 0.2 mL  

Serum 0.2 mL 

Note 1 – serum is useful to aid interpretation, but do not delay sending fluid if serum is not available. 

Note 2 – please centrifuge bloodstained or contaminated fluids as soon as possible and send supernatant. Please ring if further advice required. 

Cost 

 

£42.00 

 

Beta trace protein and/or beta 2 transferrin will be analysed depending on sample/results. Cost fixed regardless of assay(s) performed. 

Transport 

 

First class post 

 

Frequency of Analysis/Turnaround Time 

2 Working Days 

Assay Method 

Electrophoresis followed by immunoblotting 

 

Reference Range & Units 

Apart from CSF, body fluids do not normally contain beta 2 transferrin. 

 

Factors Affecting Performance of Examination 

 

Heavily blood stained samples 

Bacterial contamination 

Related Tests 

Beta trace protein 

Note - Beta Trace Protein (BTP) is the first-line screening test. 

Accredited Assay 

 

UKAS 8642 

External Quality Assurance (EQA) 

UK NEQAS for CSF B2 Transferrin/Beta Trace Protein 

Further Information 

 

emailwcf-tr.neurobiochemistry@nhs.net 

 

Telephone: 0151 5563262 

 

References 

Keir et al (1992) Immunoblotting of transferrin in the identification of cerebrospinal fluid otorrhoea and rhinorrhoea. Ann Clin Biochem 1992: 29: 210-213 

Zervos TM, Macki M, Cook B, Schultz LR, Rock JP, Craig JR. Beta-2 transferrin is detectable for 14 days whether refrigerated or stored at room temperature. International forum of Allergy and Rhinology 2018; XX: 1-4. 

Date last updated 

Tuesday, 17 August 2021 

Carbamazepine (Tegretol)

Carbamazepine  

Also known as 

CBZ, Tegretol 

Assay Information 

Please contact laboratory for details 

Specimen Type(s) & Minimum Volume 

Serum 

100 µL 

Cost 

£12.50 

Storage/Transport 

 

Store at 4ºC 

Transport by post, ambient temperature 

 

Frequency of Analysis/Turnaround Time 

 

2 working days 

Same day analysis is usually possible by prior arrangement with the lab, and if the sample is received before 12 noon. 

 

Assay Method 

UPLC-MS/MS 

 

Reference Range & Units 

4-12 mg/L  

Factors Affecting Performance of Examination 

No known analytical interferents 

Related Tests 

Carbamazepine-10,11-epoxide 

This is the pharmacologically active metabolite of carbamazepine, which may be increased with concurrent use of certain other anticonvulsants. 

Accredited Assay 

8642 

External Quality Assurance (EQA) 

 

  • LGC TDM proficiency testing scheme 

 

Further Information 

emailwcf-tr.neurobiochemistry@nhs.net 

Telephone: 0151 5563262 

References 

Antiepileptic drugs – best practice guidelines for therapeutic drug monitoring: A position paper by the sub-commission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Patsalos et al. Epilepsia 2008; 49 (7): 1239-1276. 

Date last updated 

12/08/2021 

Carbamazepine-10,11-epoxide

Carbamazepine epoxide

Also known as 

Carbamazepine epoxide

Assay Information 

Please contact laboratory for details 

Specimen Type(s) & Minimum Volume 

Serum 

100 µL 

Cost 

£12.50 

Storage/Transport 

 

Store at 4ºC 

Transport by post, ambient temperature 

 

Frequency of Analysis/Turnaround Time 

 

2 working days 

Same day analysis is usually possible by prior arrangement with the lab, and if the sample is received before 12 noon. 

 

Assay Method 

UPLC-MS/MS 

 

Reference Range & Units 

An evidence based target range for carbamazepine-10,11-epoxide has not been fully validated. However, steady state concentrations are expected in the range 0.4-4.0 mg/L, and toxic symptoms have been reported when concentrations reach 8 mg/L.

Factors Affecting Performance of Examination 

No known analytical interferents 

Related Tests 

Carbamazepine

 

Accredited Assay 

8642 

External Quality Assurance (EQA) 

 

  • LGC TDM proficiency testing scheme 

 

Further Information 

emailwcf-tr.neurobiochemistry@nhs.net 

Telephone: 0151 5563262 

References 

Antiepileptic drugs – best practice guidelines for therapeutic drug monitoring: A position paper by the sub-commission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Patsalos et al. Epilepsia 2008; 49 (7): 1239-1276.

https://www.mayocliniclabs.com/test-catalog (accessed 16/08/2021)

Date last updated 

16/08/2021 

CSF bilirubin

CSF bilirubin (Xanthochromia) 

Assay Information 

Following haemorrhage into the CSF, red blood cells undergo lysis and phagocytosis; the liberated oxyhaemoglobin is converted in-vivo in a time-dependant manner into bilirubin and sometimes methaemoglobin. Of these pigments, only bilirubin arises solely from in-vivo conversion. Oxyhaemoglobin (and possibly methaemoglobin) may both be produced in-vivo and in-vitro following a traumatic tap. Spectrophotometry is of particular value in the investigation of a CSF with an increased red cell count as there is no other reliable way of distinguishing between SAH and a traumatic tap. It is also of value in the investigation of CSF with a normal red cell count from a patient presenting several days after an event by which time the cells may no longer be present.  The presence of excess bilirubin in the CSF is calculated by measuring its Net Bilirubin Absorbance (NBA). 

 

CT scan is the primary method of detecting SAH. However, spectrophotometry of CSF is a useful second line test in patients presenting at late time points or when clinical suspicion is still high following a negative CT scan.   

 

Only patients with a negative or equivocal CT result and also with a history suggestive of SAH should be considered for LP to rule out SAH by spectrophotometry. Furthermore the LP should be at least 12hrs-post event, LP’s less than 12hrs are not diagnostic when detecting bilirubin. 

Specimen Type(s) & Minimum Volume 

CSF – 0.3 mL 

Note - Minimum volume required for assay is approximately 80uL. 

Cost 

£21.00 

Transport 

 

First class post (protected from light) 

 

Frequency of Analysis/Turnaround Time 

2 Hours 

Assay Method 

Spectrophotometry  

Reference Range & Units 

 

 

Net Bilirubin Absorbance ≤0.007 AU 

Net Oxyhaemoglobin Absorbance ≤0.02 AU 

Factors Affecting Performance of Examination 

 

 

Failure to protect from light 

Time of sampling must be >12 hours and <14 days post event. 

Delayed analysis. 

Related Tests 

Not applicable 

Accredited Assay 

 

UKAS 8642 

 

External Quality Assurance (EQA) 

UK NEQAS for immunology scheme for CSF Haem pigments 

Further Information 

 

emailwcf-tr.neurobiochemistry@nhs.net 

Telephone: 0151 5563262 

 

References 

 

Revised National Guidelines for the analysis of cerebrospinal fluid for bilirubin in suspected subarachnoid haemorrhage. Ann Clin Biochem 2008; 45: 238-244 

 

Date last updated 

Tuesday, 17 August 2021 

CSF IgG

CSF Immunoglobulin G (IgG) 

Assay Information 

 

Immunoglobulins are formed by plasma cells as a humoral response to contact of the immune system with antigens. Quantitative determination of the immunoglobulins can provide important information on the humoral immune status. Decreased serum immunoglobulin concentrations occur in primary immunodeficiency conditions as well as in secondary immune insufficiencies. Increased serum immunoglobulin concentrations occur due to polyclonal or Oligoclonal Ig proliferation. Monoclonal immunoglobulinaemia requires detailed differential diagnostic investigations in addition to quantitative determination. Local immune reactions within the CNS result in elevated immunoglobulin levels particularly IgG in the CSF.  

 

Proteins contained in human body fluids form immune complexes in an immunochemical reaction with specific antibodies. These complexes scatter a beam of light passed through the sample. The intensity of the scattered light is proportional to the concentration of the relevant protein in the sample. The result is evaluated by comparison with a standard of known concentration. 

Specimen Type(s) & Minimum Volume 

CSF - 0.2mL 

Cost 

 

CSF IgG is analysed as part of an oligoclonal bands request. Contact laboratory if just CSF IgG required. 

 

Transport 

 

First class post 

 

Frequency of Analysis/Turnaround Time 

CSF IgG analysed daily. Oligoclonal band assay TAT is 5 working days. 

Assay Method 

Nephelometry  

 

Reference Range & Units 

CSF IgG <0.034 g/L 

 

Factors Affecting Performance of Examination 

 

None 

Related Tests 

Oligoclonal bands 

CSF Index (Calculated value providing indication of likelihood of intrathecal IgG synthesis) 

Accredited Assay 

 

UKAS 8642 

 

External Quality Assurance (EQA) 

 

UK NEQAS for immunology scheme for CSF proteins & biochemistry 

Further Information 

 

emailwcf-tr.neurobiochemistry@nhs.net 

 

Telephone: 0151 5563262 

 

References 

 

To follow  

 

Date last updated 

Tuesday, 17 August 2021 

CSF Lactate

LACTATE (CSF) 

Assay Information 

 

Lactate levels in CSF are increased in bacterial meningitis, hypocapnia hydrocephalus, brain abscesses, cerebral ischemia and other conditions associated with reduced oxygenation of the brain and/or increased intracranial pressure. Measurement of CSF lactate helps in differential diagnosis between bacterial and viral infections. 

Lactate is oxidized to pyruvate and hydrogen peroxide by lactate oxidase (LOD). In the presence of peroxidase (POD), hydrogen peroxide reacts with H donor and 4-aminoantipyrine (4-AAP) to form a red quinoneimine dye. Colourimetric assay. L-lactate is oxidized to pyruvate by the specific enzyme lactate oxidase (LOD). Peroxidase (POD) is used to generate a colored dye using the hydrogen peroxide generated in the first reaction. The intensity of the color formed is directly proportional to the L-lactate concentration. It is determined by measuring the increase in absorbance. 

 

Specimen Type(s) & Minimum Volume 

CSF - 0.3mL 

Cost 

 

£17.30 

 

Transport 

 

First class post 

 

Frequency of Analysis/Turnaround Time 

Daily. Turnaround time 2 hours. 

Assay Method 

 

Colorimetric assay  

 

Reference Range & Units 

 

1.1 – 2.4 mmol/L 

 

 

 

Factors Affecting Performance of Examination 

 

Ensure sample is acellular. Please centrifuge and send supernatant if cells present. 

Related Tests 

None 

 

Accredited Assay 

 

UKAS 8642 

 

External Quality Assurance (EQA) 

 

  • UK NEQAS for CSF Proteins and Biochemistry  

Further Information 

 

emailwcf-tr.neurobiochemistry@nhs.net 

 

Telephone: 0151 5563262 

 

References 

 

To follow 

Date last updated 

 

15th August 2021 

 

Free Phenytoin (Dilantin)

Free phenytoin  

Also known as 

Unbound phenytoin, Dilantin, Epanutin 

Assay Information 

 

Includes measurement of total phenytoin. 

Please contact laboratory for details. 

 

Specimen Type(s) & Minimum Volume 

Serum 

500 µL 

Cost 

£25.00 

Storage/Transport 

 

Store at 4ºC 

Transport by post, ambient temperature 

 

Frequency of Analysis/Turnaround Time 

 

2 working days 

Same day analysis is usually possible by prior arrangement with the lab, and if the sample is received before 12 noon. 

 

Assay Method 

UPLC-MS/MS 

 

Reference Range & Units 

 

0.5-2 mg/L  

This range is 10% of the total phenytoin range quoted by the National Pathology Harmony Group (www.pathologyharmony.co.uk) 

 

Factors Affecting Performance of Examination 

No known analytical interferents 

Related Tests 

Phenytoin 

 

Accredited Assay 

8642 

External Quality Assurance (EQA) 

 

  • LGC TDM proficiency testing scheme 

 

Further Information 

emailwcf-tr.neurobiochemistry@nhs.net 

Telephone: 0151 5563262 

References 

Antiepileptic drugs – best practice guidelines for therapeutic drug monitoring: A position paper by the sub-commission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Patsalos et al. Epilepsia 2008; 49 (7): 1239-1276. 

Date last updated 

16/08/2021 

Lamotrigine (Lamictal)

Lamotrigine  

Also known as 

Lamictal 

Assay Information 

 

Please contact laboratory for details. 

 

Specimen Type(s) & Minimum Volume 

Serum 

100 µL 

Cost 

£12.50 

Storage/Transport 

 

Store at 4ºC 

Transport by post, ambient temperature 

 

Frequency of Analysis/Turnaround Time 

 

2 working days 

Same day analysis is usually possible by prior arrangement with the lab, and if the sample is received before 12 noon. 

 

Assay Method 

UPLC-MS/MS 

 

Reference Range & Units 

3-15 mg/L 

Factors Affecting Performance of Examination 

No known analytical interferents 

Related Tests 

None 

 

Accredited Assay 

8642 

External Quality Assurance (EQA) 

 

  • LGC TDM proficiency testing scheme 

 

Further Information 

emailwcf-tr.neurobiochemistry@nhs.net 

Telephone: 0151 5563262 

References 

Antiepileptic drugs – best practice guidelines for therapeutic drug monitoring: A position paper by the sub-commission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Patsalos et al. Epilepsia 2008; 49 (7): 1239-1276. 

Date last updated 

16/08/2021 

Levetiracetam (Keppra)

 

Levetiracetam

Also known as

Keppra

Assay Information

Please contact laboratory for details

Specimen Type(s) & Minimum Volume

Serum

100 µL

Cost

£30.00

Storage/Transport

 

Store at 4ºC

Transport by post, ambient temperature

 

Frequency of Analysis/Turnaround Time

 

5 working days

Same day analysis is usually possible by prior arrangement with the lab, and if the sample is received before 12 noon.

 

Assay Method

UPLC-MS/MS

 

Reference Range & Units

12-46 mg/L

Factors Affecting Performance of Examination

No known analytical interferents

Related Tests

 

 

Accredited Assay

8642

External Quality Assurance (EQA)

 

  • LGC TDM proficiency testing scheme

 

Further Information

email: wcf-tr.neurobiochemistry@nhs.net

Telephone: 0151 5563262

References

Antiepileptic drugs – best practice guidelines for therapeutic drug monitoring: A position paper by the sub-commission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Patsalos et al. Epilepsia 2008; 49 (7): 1239-1276.

Date last updated

16/08/2021

Midazolam

Midazolam 

Also known as 

 

Assay Information 

Please contact laboratory for details 

Specimen Type(s) & Minimum Volume 

Serum 

100 µL 

Cost 

£50.00 

Storage/Transport 

 

Store at 4ºC 

Transport by post, ambient temperature. 

 

Frequency of Analysis/Turnaround Time 

 

1 working day 

Same day analysis is usually possible by prior arrangement with the lab, and if the sample is received before 12 noon. 

 

Assay Method 

UPLC-MS/MS 

 

Reference Range & Units 

 

If the serum midazolam concentration is being measured as part of brain stem death testing, no further testing should be undertaken unless the midazolam concentration is less than 10µg/L. 

 

Factors Affecting Performance of Examination 

No known analytical interferents 

Related Tests 

None 

 

Accredited Assay 

8642 

External Quality Assurance (EQA) 

 

  • LGC TOX proficiency testing scheme 

 

Further Information 

emailwcf-tr.neurobiochemistry@nhs.net 

Telephone: 0151 5563262 

References 

 

Academy of Medical Royal Colleges. A code of practice for the diagnosis and confirmation of death. 2008. 

 

Date last updated 

16/08/2021 

Oligoclonal bands

Oligoclonal bands (CSF) 

Assay Information 

Multiple sclerosis (MS) is an autoimmune condition in which the immune system attacks the CNS, leading to demyelination. It causes numerous physical symptoms, and often progresses to physical and cognitive disability. Disease onset usually occurs in young adults, is more common in women, and has a prevalence that ranges between 2 and 150 per 100,000 depending on the country or specific population. 

 

MS affects the areas of the brain and spinal cord known as the white matter, specifically,  destroying oligodendrocytes which are the cells responsible for creating and maintaining the myelin sheath, which helps the neurons carry electrical signals. MS results in a thinning or complete loss of myelin and, less frequently, the cutting (transection) of the neurons axons. When the myelin is lost, the neurons can no longer effectively conduct their electrical signals. The name “multiple sclerosis” refers to the scars (scleroses - better known as plaques or lesions) in the white matter. Loss of myelin in these lesions causes some of the symptoms, which vary widely depending upon which signals are interrupted. However, more advanced forms of imaging are now showing that much of the damage happens outside these regions. Almost any neurological symptom can accompany the disease. 

 

Immunoglobulins can be separated according to their isoelectric points within a pH gradient that is generated by electrophoresis and stabilised using zwitterionic ampholytes (Pharmalytes). Once separated the proteins are passively transferred onto a nitrocellulose membrane. Unoccupied protein binding sites are blocked with non-fat milk. Immunoglobulin G is identified using a single antibody detection system, using a goat anti-human IgG peroxidase conjugate antibody. Bound peroxidase activity is detected by a chromogenic reaction utilising amino-ethyl-carbazole and 30% v/v Hydrogen peroxide. This results in a pink-brown precipitate that corresponds to the separated immunoglobulin G from the original sample. 

 

Isoelectric focusing is used by the Neuroimmunology laboratory to detect oligoclonal IgG responses in cerebrospinal fluid (CSF) and serum. The principal purpose of the examination is to identify those patients that have oligoclonal bands in the CSF only, with no corresponding bands in paired serum. The oligoclonal bands (OCB) are thus local to the central nervous system, and so are termed locally or intrathecally synthesised OCBs. 

 

The detection of OCB is a sensitive and specific marker for intrathecal synthesis of IgG which is present in a large proportion of patients with demyelinating diseases (>90%). In multiple sclerosis the sensitivity of OCB is thought to be >95%. Oligoclonal bands are also found in a number of other inflammatory and infectious diseases of the CNS, including paraneoplastic disease and encephalitis, although a few weak oligoclonal bands may also be present in the serum as well as CSF in such cases. 

Specimen Type(s) & Minimum Volume 

 

CSF – 0.2 mL 

Serum – 0.2 mL  

Note – CSF and serum samples required for interpretation 

Cost 

 

£38.00 

 

Transport 

 

First class post 

 

 

Frequency of Analysis/Turnaround Time 

5 working days 

Assay Method 

 

Isoelectric focusing 

 

Reference Range & Units 

 

A normal sample will contain no oligoclonal bands. 

Factors Affecting Performance of Examination 

 

Grossly haemolysed samples 

CSF and serum should be ideally be taken on same day.  

Related Tests 

CSF IgG 

CSF Index (Calculated value providing indication of likelihood of intrathecal IgG synthesis) 

Accredited Assay 

 

UKAS 8642 

 

External Quality Assurance (EQA) 

UKNEQAS CSF oligoclonal bands 

Further Information 

 

emailwcf-tr.neurobiochemistry@nhs.net 

Telephone: 0151 5563262 

 

References 

 

Keir G et al. Isoelectric Focusing of Cerebrospinal Fluid Immunoglobulin G: An Annotated Update. Ann Clin Biochem 1990; 27:436-443 

 

Andersson M et al. Cerebrospinal fluid in the diagnosis of multiple sclerosis: a consensus report. Journal of Neurology, Neurosurgery and Psychiatry 1994; 57:897-902 

 

Date last updated 

Tuesday, 17 August 2021 

Phenobarbital (Luminal)

Phenobarbital 

Also known as 

Luminal 

Assay Information 

 

Please contact laboratory for details  

 

Specimen Type(s) & Minimum Volume 

Serum - 0.1mL 

Cost 

 

£12.50 

 

Transport 

 

Store at 4ºC 

Transport by post, ambient temperature. 

 

Frequency of Analysis/Turnaround Time 

2 working days 

Same day analysis is usually possible by prior arrangement with the lab, and if the sample is received before 12 noon. 

Assay Method 

Liquid chromatography tandem mass spectrometry 

Reference Range & Units 

10-40 mg/L  

 

Factors Affecting Performance of Examination 

 

No known interferences 

 

Related Tests 

 

None 

 

Accredited Assay 

 

UKAS 8642 

 

External Quality Assurance (EQA) 

LGC Therapeutic drugs scheme antiepileptic drugs mixture 

Further Information 

 

emailwcf-tr.neurobiochemistry@nhs.net 

 

Telephone: 0151 5563262 

 

References 

 

Antiepileptic drugs – best practice guidelines for therapeutic drug monitoring: A position paper by the sub-commission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Patsalos et al. Epilepsia 2008; 49 (7): 1239-1276. 

Date last updated 

Tuesday, 17 August 2021 

Phenytoin (Dilantin)

Phenytoin  

Also known as 

Dilantin, Epanutin 

Assay Information 

 

Please contact laboratory for details. 

 

Specimen Type(s) & Minimum Volume 

Serum 

100 µL 

Cost 

£12.50 

Storage/Transport 

 

Store at 4ºC 

Transport by post, ambient temperature 

 

Frequency of Analysis/Turnaround Time 

 

2 working days 

Same day analysis is usually possible by prior arrangement with the lab, and if the sample is received before 12 noon. 

 

Assay Method 

UPLC-MS/MS 

 

Reference Range & Units 

5-20 mg/L 

Factors Affecting Performance of Examination 

No known analytical interferents 

Related Tests 

Free phenytoin 

Accredited Assay 

8642 

External Quality Assurance (EQA) 

 

  • LGC TDM proficiency testing scheme 

 

Further Information 

emailwcf-tr.neurobiochemistry@nhs.net 

Telephone: 0151 5563262 

References 

Antiepileptic drugs – best practice guidelines for therapeutic drug monitoring: A position paper by the sub-commission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Patsalos et al. Epilepsia 2008; 49 (7): 1239-1276. 

Date last updated 

16/08/2021 

Pregabalin (Lyrica)

Pregabalin  

Also known as 

Lyrica 

Assay Information 

 

Please contact laboratory for details. 

 

Specimen Type(s) & Minimum Volume 

Serum 

100 µL 

Cost 

£30.00 

Storage/Transport 

 

Store at 4ºC 

Transport by post, ambient temperature 

 

Frequency of Analysis/Turnaround Time 

 

5 working days 

Same day analysis is usually possible by prior arrangement with the lab, and if the sample is received before 12 noon. 

 

Assay Method 

UPLC-MS/MS 

 

Reference Range & Units 

 

No evidence based target range is available for pregabalin. However, results are expected in the range of 2.8-8.3 mg/L. 

 

Factors Affecting Performance of Examination 

No known analytical interferents 

Related Tests 

 

 

Accredited Assay 

8642 

External Quality Assurance (EQA) 

 

  • LGC TDM proficiency testing scheme 

 

Further Information 

emailwcf-tr.neurobiochemistry@nhs.net 

Telephone: 0151 5563262 

References 

Antiepileptic drugs – best practice guidelines for therapeutic drug monitoring: A position paper by the sub-commission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Patsalos et al. Epilepsia 2008; 49 (7): 1239-1276. 

Date last updated 

16/08/2021 

Topiramate (Topamax)

Topiramate 

Also known as 

Topamax 

Assay Information 

 

Please contact laboratory for details. 

 

Specimen Type(s) & Minimum Volume 

Serum 

100 µL 

Cost 

£30.00 

Storage/Transport 

 

Store at 4ºC 

Transport by post, ambient temperature 

 

Frequency of Analysis/Turnaround Time 

 

5 working days 

Same day analysis is usually possible by prior arrangement with the lab, and if the sample is received before 12 noon. 

 

Assay Method 

UPLC-MS/MS 

 

Reference Range & Units 

 

5-20 mg/L. 

 

Factors Affecting Performance of Examination 

No known analytical interferents 

Related Tests 

 

 

Accredited Assay 

8642 

External Quality Assurance (EQA) 

 

  • LGC TDM proficiency testing scheme 

 

Further Information 

emailwcf-tr.neurobiochemistry@nhs.net 

Telephone: 0151 5563262 

References 

Antiepileptic drugs – best practice guidelines for therapeutic drug monitoring: A position paper by the sub-commission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Patsalos et al. Epilepsia 2008; 49 (7): 1239-1276. 

Date last updated 

16/08/2021 

Valproate (Epilim)

Valproic acid  

Also known as 

Sodium valproate, Epilim 

Assay Information 

 

Please contact laboratory for details. 

 

Specimen Type(s) & Minimum Volume 

Serum 

100 µL 

Cost 

£12.50 

Storage/Transport 

 

Store at 4ºC 

Transport by post, ambient temperature 

 

Frequency of Analysis/Turnaround Time 

 

2 working days 

Same day analysis is usually possible by prior arrangement with the lab, and if the sample is received before 12 noon. 

 

Assay Method 

UPLC-MS/MS 

 

Reference Range & Units 

No evidence based target range available 

Factors Affecting Performance of Examination 

No known analytical interferents 

Related Tests 

 

 

Accredited Assay 

8642 

External Quality Assurance (EQA) 

 

  • LGC TDM proficiency testing scheme 

 

Further Information 

emailwcf-tr.neurobiochemistry@nhs.net 

Telephone: 0151 5563262 

References 

Antiepileptic drugs – best practice guidelines for therapeutic drug monitoring: A position paper by the sub-commission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Patsalos et al. Epilepsia 2008; 49 (7): 1239-1276. 

Date last updated 

16/08/2021 

Xanthochromia

 

CSF bilirubin (Xanthochromia)

Assay Information

Following haemorrhage into the CSF, red blood cells undergo lysis and phagocytosis; the liberated oxyhaemoglobin is converted in-vivo in a time-dependant manner into bilirubin and sometimes methaemoglobin. Of these pigments, only bilirubin arises solely from in-vivo conversion. Oxyhaemoglobin (and possibly methaemoglobin) may both be produced in-vivo and in-vitro following a traumatic tap. Spectrophotometry is of particular value in the investigation of a CSF with an increased red cell count as there is no other reliable way of distinguishing between SAH and a traumatic tap. It is also of value in the investigation of CSF with a normal red cell count from a patient presenting several days after an event by which time the cells may no longer be present.  The presence of excess bilirubin in the CSF is calculated by measuring its Net Bilirubin Absorbance (NBA).

 

CT scan is the primary method of detecting SAH. However, spectrophotometry of CSF is a useful second line test in patients presenting at late time points or when clinical suspicion is still high following a negative CT scan. 

 

Only patients with a negative or equivocal CT result and also with a history suggestive of SAH should be considered for LP to rule out SAH by spectrophotometry. Furthermore the LP should be at least 12hrs-post event, LP’s less than 12hrs are not diagnostic when detecting bilirubin.

Specimen Type(s) & Minimum Volume

CSF – 0.3 mL

Note - Minimum volume required for assay is approximately 80uL.

Cost

£21.00

Transport

 

First class post (protected from light)

 

Frequency of Analysis/Turnaround Time

2 Hours

Assay Method

Spectrophotometry

Reference Range & Units

 

 

Net Bilirubin Absorbance ≤0.007 AU

Net Oxyhaemoglobin Absorbance ≤0.02 AU

Factors Affecting Performance of Examination

 

 

Failure to protect from light

Time of sampling must be >12 hours and <14 days post event.

Delayed analysis.

Related Tests

Not applicable

Accredited Assay

 

UKAS 8642

 

External Quality Assurance (EQA)

UK NEQAS for immunology scheme for CSF Haem pigments

Further Information

 

email: wcf-tr.neurobiochemistry@nhs.net

Telephone: 0151 5563262

 

References

 

Revised National Guidelines for the analysis of cerebrospinal fluid for bilirubin in suspected subarachnoid haemorrhage. Ann Clin Biochem 2008; 45: 238-244

 

Date last updated

Monday, 06 September 2021

 

Page last updated: 21 September 2021