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Beta trace protein

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	email: wcf-tr.neurobiochemistry@nhs.net Telephone: 0151 5563262
References	Bernasconi L, P ȍ tzl 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	email: wcf-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	Anti-epileptic drugs (AEDs) are prescribed to patients with epilepsy to aid in seizure control. Measuring serum concentrations of AEDs can have a valuable role in guiding patient management. Pre-dose specimens are advisable for monitoring, although not essential. Measurement by UPLC-MS/MS employs a chromatographic step to separate out the sample components, followed by quantitation using a tandem mass spectrometer. This combination of techniques ensures high sensitivity detection and excellent specificity for the compound of interest.
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	Results >25 mg/L will be telephoned to the requesting location.
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	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	03/11/2025

Carbamazepine-10,11-epoxide

**Carbamazepine epoxide**
Also known as	Carbamazepine epoxide
Assay Information	Anti-epileptic drugs (AEDs) are prescribed to patients with epilepsy to aid in seizure control. Measuring serum concentrations of AEDs can have a valuable role in guiding patient management. Pre-dose specimens are advisable for monitoring, although not essential. Measurement by UPLC-MS/MS employs a chromatographic step to separate out the sample components, followed by quantitation using a tandem mass spectrometer. This combination of techniques ensures high sensitivity detection and excellent specificity for the compound of interest. Carbamazepine-10,11-epoxide is the active metabolite of carbamazepine, and can accumulate to concentrations associated with toxicity. Measurement of carbamazepine-10,11-epoxide is therefore of particular use in patients who show signs of carbamazepine toxicity, but whose serum carbamazepine concentration is within the therapeutic range.
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	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. https://www.mayocliniclabs.com/test-catalog (accessed 16/08/2021)
Date last updated	03/11/2025

CSF bilirubin

**CSF bilirubin (Xanthochromia)**
Assay Information	Bilirubin is the end product in the breakdown of haem, produced in vivo from red cell breakdown after haemorrhage into the CSF. It can therefore be measured to aid in the diagnosis of subarachnoid haemorrhage (SAH) in patients who have had a negative or equivocal CT scan result, or when the patient presents several days after a potential event. Following haemorrhage into the CSF, red blood cells release oxyhaemoglobin, which is converted into bilirubin in a time-dependent manner. Oxyhaemoglobin may also be released into the CSF during the sampling procedure, but due to the time taken for bilirubin to be produced, its measurement in CSF can distinguish reliably between SAH and a traumatic tap. Measurement of CSF bilirubin is also of value in the investigation of CSF with a normal red cell count, collected from a patient presenting several days after an event; by this time the cells may no longer be present but bilirubin may still be detected. Only patients with a negative or equivocal CT result and with a history suggestive of SAH should be considered for lumbar puncture to rule out SAH by spectrophotometry. Samples should be collected at least 12 hours post-event; samples collected before this time may give false negative results, as the conversion of oxyhaemoglobin to bilirubin is time-dependent. Samples collected >14 days post-event may also give false negative results, due to in vivo clearance of bilirubin from the CSF. CSF bilirubin may also be detectable in conditions such as meningitis or spontaneous intracranial hypotension.
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	03/11/2025

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 - 0.3mL
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 7 working days.
Assay Method	Nephelometry
Reference Range & Units	CSF IgG 0.01-0.04 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	email : wcf-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 Wildemann B, Oschmann P, Reiber H. Laboratory Diagnosis in Neurology 2010 Chapter 21 doi: 10.1055/b-022-80425
Date last updated	03/11/2025

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 coloured dye using the hydrogen peroxide generated in the first reaction. The intensity of the colour 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	1.01 - 2.09 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	email : wcf-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	Phenytoin is a highly protein-bound anti-epileptic drug with a narrow therapeutic index. Symptoms of toxicity can be similar to those of sub-therapeutic dosage. In the majority of patients treated with phenytoin, the total serum concentration correlates well with the observed effect. However, in patients with abnormal serum protein concentration, or who are treated with multiple agents that may displace phenytoin from binding proteins, correlation may not be observed. In these cases, measurement of the unbound, pharmacologically active phenytoin is advised, as it has a better correlation with clinical effects/toxicity. Although the free phenytoin concentration may be estimated using various equations, we have found that the results of these are often negatively biased when compared with the measured free phenytoin result. This could have a significant clinical impact on the management of some patients. Patients with a total phenytoin concentration ≤2 mg/L do not require free phenytoin measurement. Assay includes measurement of total phenytoin. Please contact laboratory for further details and advice.
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 https://labmed.org.uk/resource/pathology-harmony---biochemistry.html
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	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. Assessment of the accuracy of estimated free phenytoin concentrations in a mixed patient population. Horton et al. Eur J Hosp Pharm 2023; https://doi.org/10.1136/ejhpharm-2023-003878
Date last updated	03/11/2025

Lamotrigine (Lamictal)

**Lamotrigine**
Also known as	Lamictal
Assay Information	Anti-epileptic drugs (AEDs) are prescribed to patients with epilepsy to aid in seizure control. Measuring serum concentrations of AEDs can have a valuable role in guiding patient management. Pre-dose specimens are advisable for monitoring, although not essential. Measurement by UPLC-MS/MS employs a chromatographic step to separate out the sample components, followed by quantitation using a tandem mass spectrometer. This combination of techniques ensures high sensitivity detection and excellent specificity for the compound of interest.
Specimen Type(s) & Minimum Volume	Serum 100 µL
Cost	£17.00
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	3-15 mg/L Results >25 mg/L will be telephoned to the requesting location
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	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. Acute lamotrigine overdose: a systematic review of published adult and pediatric cases. Alyahya et al. Clinical Toxicology 2018; 56 (2): 81-89
Date last updated	03/11/2025

Levetiracetam (Keppra)

**Levetiracetam**
Also known as	Keppra
Assay Information	Anti-epileptic drugs (AEDs) are prescribed to patients with epilepsy to aid in seizure control. Measuring serum concentrations of AEDs can have a valuable role in guiding patient management. Pre-dose specimens are advisable for monitoring, although not essential. Measurement by UPLC-MS/MS employs a chromatographic step to separate out the sample components, followed by quantitation using a tandem mass spectrometer. This combination of techniques ensures high sensitivity detection and excellent specificity for the compound of interest
Specimen Type(s) & Minimum Volume	Serum 100 µL
Cost	£17.00
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	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	03/11/2025

Midazolam

**Midazolam**
Also known as
Assay Information	Midazolam is a benzodiazepine drug used as a sedative in intensive care units. If midazolam has previously been prescribed to a comatose patient, brain stem death can only be investigated once the patient’s serum midazolam concentration has fallen to <10 µg/L. Measurement by UPLC-MS/MS employs a chromatographic step to separate out the sample components, followed by quantitation using a tandem mass spectrometer. This combination of techniques ensures high sensitivity detection and excellent specificity for the compound of interest.
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	email: wcf-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	03/11/2025

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 – 0.3 mL Serum – 0.3 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	email : wcf-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	Anti-epileptic drugs (AEDs) are prescribed to patients with epilepsy to aid in seizure control. Measuring serum concentrations of AEDs can have a valuable role in guiding patient management. Pre-dose specimens are advisable for monitoring, although not essential. Measurement by UPLC-MS/MS employs a chromatographic step to separate out the sample components, followed by quantitation using a tandem mass spectrometer. This combination of techniques ensures high sensitivity detection and excellent specificity for the compound of interest.
Specimen Type(s) & Minimum Volume	Serum 100 µL
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 Results >70 mg/L will be phoned to the requestor
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	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	03/11/2025

Phenytoin (Dilantin)

**Phenytoin**
Also known as	Dilantin, Epanutin
Assay Information	Phenytoin is an anti-epileptic drug with a narrow therapeutic index. Symptoms of toxicity can be similar to those of sub-therapeutic dosage. Phenytoin metabolism is saturable and the concentration at which saturation occurs varies between individuals; minor changes in dosage can therefore result in significant changes in serum concentration. Monitoring is recommended on initiation of treatment, if dosage is changed or other medications are added. Phenytoin concentration should also be measured if there is inadequate seizure control, or there is a deterioration in control. Free (non-protein bound) phenytoin can also be measured in complex cases.
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 Results >25 mg/L will be telephoned to the requesting location.
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	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	03/11/2025

Pregabalin (Lyrica)

**Pregabalin**
Also known as	Lyrica
Assay Information	Anti-epileptic drugs (AEDs) are prescribed to patients with epilepsy to aid in seizure control. Measuring serum concentrations of AEDs can have a valuable role in guiding patient management. Pre-dose specimens are advisable for monitoring, although not essential. Measurement by UPLC-MS/MS employs a chromatographic step to separate out the sample components, followed by quantitation using a tandem mass spectrometer. This combination of techniques ensures high sensitivity detection and excellent specificity for the compound of interest.
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	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	03/11/2025

Topiramate (Topamax)

**Topiramate**
Also known as	Topamax
Assay Information	Anti-epileptic drugs (AEDs) are prescribed to patients with epilepsy to aid in seizure control. Measuring serum concentrations of AEDs can have a valuable role in guiding patient management. Pre-dose specimens are advisable for monitoring, although not essential. Measurement by UPLC-MS/MS employs a chromatographic step to separate out the sample components, followed by quantitation using a tandem mass spectrometer. This combination of techniques ensures high sensitivity detection and excellent specificity for the compound of interest.
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	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	03/11/2025

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	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

Xanthochromia

**CSF bilirubin (Xanthochromia)**
Assay Information	Bilirubin is the end product in the breakdown of haem, produced in vivo from red cell breakdown after haemorrhage into the CSF. It can therefore be measured to aid in the diagnosis of subarachnoid haemorrhage (SAH) in patients who have had a negative or equivocal CT scan result, or when the patient presents several days after a potential event. Following haemorrhage into the CSF, red blood cells release oxyhaemoglobin, which is converted into bilirubin in a time-dependent manner. Oxyhaemoglobin may also be released into the CSF during the sampling procedure, but due to the time taken for bilirubin to be produced, its measurement in CSF can distinguish reliably between SAH and a traumatic tap. Measurement of CSF bilirubin is also of value in the investigation of CSF with a normal red cell count, collected from a patient presenting several days after an event; by this time the cells may no longer be present but bilirubin may still be detected. Only patients with a negative or equivocal CT result and with a history suggestive of SAH should be considered for lumbar puncture to rule out SAH by spectrophotometry. Samples should be collected at least 12 hours post-event; samples collected before this time may give false negative results, as the conversion of oxyhaemoglobin to bilirubin is time-dependent. Samples collected >14 days post-event may also give false negative results, due to in vivo clearance of bilirubin from the CSF. CSF bilirubin may also be detectable in conditions such as meningitis or spontaneous intracranial hypotension.
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	03/11/2025