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Coenzyme Q10 (CoQ10) is an essential cofactor in the mitochondrial respiratory chain responsible for oxidative phosphorylation, where it functions as an electron carrier and acts as an antioxidant. It is found in all cell membranes and is carried by lipoproteins in the circulation. Approximately 60% of CoQ10 is associated with low-density lipoprotein (LDL), 25% with high-density lipoprotein (HDL), and 15% with other lipoproteins. CoQ10 is present in the body in both the reduced and oxidized forms, with the antioxidant activity of CoQ10 dependent not only on its concentration, but also on its reduction-oxidation (redox) status.
Primary CoQ10 deficiency, although rare, is characterized by neurological symptoms (seizures, developmental delay, ataxia, etc) and muscle weakness. At least 5 different phenotypes of primary CoQ10 deficiency have been described:
-Encephalomyopathy (elevated serum creatine kinase [CK], recurrent myoglobinuria, lactic acidosis)
-Childhood-onset cerebellar ataxia and atrophy (neuropathy, hypogonadism)
-Multisystemic infant form (nystagmus, optic atrophy, sensorineural hearing loss, dystonia, rapidly progressing nephropathy)
-Myopathy (exercise intolerance, fatigue, elevated serum CK)
Treatment with CoQ10 in patients with mitochondrial cytopathies can improve mitochondrial respiration in both brain and skeletal muscle.
CoQ10 has been implicated in other disease processes, including Parkinson disease, diabetes, and Alzheimer disease, as well as in aging and oxidative stress. CoQ10 may also play a role in hydroxymethylglutaryl-CoA reductase inhibitor (statin) therapy; changes in CoQ10 may be relevant to statin-induced myalgia. The redox status of CoQ10 may be a useful early marker for the detection of oxidative LDL modification.
Diagnosis of coenzyme Q10 (CoQ10) deficiency in mitochondrial disorders
Monitoring patients receiving statin therapy
Monitoring CoQ10 status during treatment of various degenerative conditions including Parkinson and Alzheimer disease
Abnormal results are reported with a detailed interpretation including an overview of the results and their significance, a correlation to available clinical information provided with the specimen, differential diagnosis, and recommendations for additional testing when indicated and available, and a phone number to reach a laboratory director in case the referring physician has additional questions.
Coenzyme Q10 (CoQ10) is sensitive to specimen handling and transport temperature. Failure to follow the specimen handling and transportation recommendations may lead to false-positive results.
<18 years: 320-1,376 mcg/L
> or =18 years: 415-1,480 mcg/L
<18 years: 320-1,558 mcg/L
> or =18 years: 433-1,532 mcg/L
% REDUCED CoQ10
<18 years: 93-100%
> or =18 years: 92-98%
Miles MV, Horn PS, Tang PH, et al: Age-related changes in plasma coenzyme Q10 concentrations and redox state in apparently healthy children and adults. Clin Chim Acta 2004;34:139-144
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2. Miles MV, Horn PS, Morrison JA, et al: Plasma coenzyme Q10 reference intervals, but not redox status, are affected by gender and race in self-reported healthy adults. Clin Chim Acta 2003 June;332(1-2):123-132
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4. Steele PE, Tang PH, DeGrauw AJ, Miles MV: Clinical laboratory monitoring of coenzyme Q10 use in neurologic and muscular diseases. Am J Clin Pathol 2004 June;121:S113-S120