Analysis of coenzyme Q10 in lymphocytes by HPLC–MS/MS

Coenzyme Q10 (CoQ10) deficiency syndromes are potentially treatable disorders. Skeletal muscle is the most widely accepted tissue for their study, but sampling is an invasive procedure. Cultured skin fibroblasts seem to improve the biochemical diagnosis, but their growth requires a certain period of time. Our aim was to set up a minimally invasive, fast and reliable analytical procedure to measure CoQ10 in lymphocytes, to prevent any delay in diagnosing primary CoQ10 deficiency. HPLC–MS/MS analysis of CoQ10 showed high sensitivity and specificity. The reference range was established in apparently healthy volunteers (n = 33); the mean of CoQ10 in lymphocytes was 107 nmol/g protein (95% confidence interval: 105–120) and 2.0 nmol/UCS (95% confidence interval: 2.06–2.46). Therefore, the range was narrower when normalized to units of citrate synthase (UCS) than when normalized to grams of protein. The method was linear from 0.01 to 1 μM with a good precision and sensitivity (limit of quantification 0.01 μM). Intra-assay and inter-assay coefficients of variation were lower than 13%. Recovery was higher than 95%. In our hands, lymphocytes seem to be a reliable matrix as they reflect intracellular content of CoQ10. In addition, they can be obtained by a minimally invasive procedure (venipuncture).