Carnitine (free and total), urine
Clinical Background:
Carnitine is required for transport of long-chain fatty acids into the mitochondria for β-oxidation. Primary carnitine deficiency is caused by impaired function of the carnitine transporter protei...
Carnitine is required for transport of long-chain fatty acids into the mitochondria for β-oxidation. Primary carnitine deficiency is caused by impaired function of the carnitine transporter protein OCTN2 resulting in renal loss of carnitine, low plasma concentrations and low intracellular carnitine potentially leading to impaired fatty acid oxidation.
Measurement of paired urine and plasma free & total carnitine is used in the investigation of primary carnitine deficiency. Calculation of tubular reabsorption of carnitine can determine whether there is increased renal loss of carnitine. Plasma and urine creatinine results are also required for this calculation; these can be measured at NuTH if results are not provided with the request.
Test Details
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Discipline:
Biochemistry
Biochemistry
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Specimen Container Adult:
Plain universal container
Plain universal container
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Specimen Container Paediatric:
Plain universal container
Plain universal container
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Minimum Volume Adult:
3 mL urine
3 mL urine
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Minimum Volume Paediatric:
5 mL urine
5 mL urine
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Sample Stability:
Free and total carnitine is stable at -20°C for up to 3 months and at -80°C for up to 6 months
Free and total carnitine is stable at -20°C for up to 3 months and at -80°C for up to 6 months
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Transport Requirements:
Samples may be sent by 1st class post to reach the laboratory within 48 hours of collection.
On arrival samples should be stored at -20°C or lower if there is a delay in analysis.
Samples may be sent by 1st class post to reach the laboratory within 48 hours of collection.
On arrival samples should be stored at -20°C or lower if there is a delay in analysis.
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Interpretation:
Carnitine is required for the transfer of long-chain fatty acids into mitochondria for b-oxidation. Carnitine also facilitates the removal of excess acyl-CoA esters (i.e. intermediates of fatty aci...
Read MoreCarnitine is required for the transfer of long-chain fatty acids into mitochondria for b-oxidation. Carnitine also facilitates the removal of excess acyl-CoA esters (i.e. intermediates of fatty acids oxidation, branched-chain amino acid metabolism and drug metabolites) out of the mitochondrial compartment for detoxification and excretion in the urine. Inborn errors of metabolism in which acyl-CoA esters accumulate are associated with increased acylcarnitine concentrations in tissues and blood, and greatly increased urinary excretion of acylcarnitines. The increased excretion of acylcarnitines in the urine is also associated with the excessive loss of free carnitine (inhibition of tubular reabsorption). The chronic loss of free and acylated carnitine into the urine can lead to depletion of tissue stores of L-carnitine and secondary carnitine deficiency. Primary carnitine deficiency is an inborn defect of carnitine uptake into tissues and cells. Patients with this condition have very low levels of tissue and plasma free carnitine and total carnitine. The relative distribution of free carnitine and carnitine esters may vary according to fasting status, renal function, muscular exercise and as a result of a defect of acyl-CoA metabolism. Acylcarnitine fraction tends to increase with fasting or under the conditions of catabolic stress.
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Reference Ranges:
Free carnitine: 3.0 - 146.0 mmol/mol creatinine
Total carnitine: 12.0 - 294.0 mmol/mol creatinine
% Acylated: 20 – 75
...Read MoreFree carnitine: 3.0 - 146.0 mmol/mol creatinine
Total carnitine: 12.0 - 294.0 mmol/mol creatinine
% Acylated: 20 – 75
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Routine Contact Name:
Duty biochemist
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Routine Telephone:
Freeman: 0191 244 8889
RVI: 0191 282 9719
Freeman: 0191 244 8889
RVI: 0191 282 9719
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Routine Email:
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Specialist Test:
Yes
Yes
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Specialist Contact Name:
Metabolic Clinical Scientist
Metabolic Clinical Scientist
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Specialist Telephone:
0191 282 9685 (Consultant Clinical Scientist)
0191 282 0334 (Metabolic Laboratory)
0191 282 9685 (Consultant Clinical Scientist)
0191 282 0334 (Metabolic Laboratory)
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Specialist Email: