Test ID: Q10
Coenzyme Q10, Reduced and Total, Plasma

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

Monitoring coenzyme Q10 status in patients receiving statin therapy or during treatment of various degenerative conditions including Parkinson and Alzheimer disease. Freeze plasma within 3 hours of blood collection to limit oxidation of the reduced form of coenzyme Q10.

Coenzyme Q10 (CoQ10) is an essential cofactor in the mitochondrial respiratory chain responsible for oxidative phosphorylation, where it functions as an electron carrier in the lipid phase of the mitochondrial membrane. The reversible oxidation and reduction of CoQ10 is the basis for its function as a carrier of electrons between flavoproteins and cytochromes. The low potential required for oxidation or reduction of this compound makes it possible to fulfill its pivotal role in the electron transport chain.

CoQ10 also has a major function as an antioxidant. It is found in all cell membranes and 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 exercise intolerance, recurrent myoglobinuria, developmental delay, ataxia, and seizures. At least 5 different phenotypes have been described:

-A myopathic form with myoglobinuria

-Epilepsy and ataxia

-Severe infantile syndrome with encephalopathy and renal disease

-An ataxic form presenting with cerebellar atrophy (includes neonatal fatal form, Leigh syndrome in adulthood)

-Liver failure plus Leigh syndrome

Treatment with CoQ10 in patients with mitochondrial cytopathies improves 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.

CoQ10 REDUCED

<18 years: 320-1,376 mcg/L

> or =18 years: 415-1,480 mcg/L

TOTAL CoQ10

<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

When abnormal results are detected, a detailed interpretation is provided that includes an overview of the results, their significance, and recommendations for follow-up testing.

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.

1. 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

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