Respiratory chain and pyruvate metabolism deficiencies in pediatric patients: Evaluation of biochemical tests for selective screening

Introduction. The correct selection of pediatric patients with clinical suspicion of mitochondrial diseases is the first step to achieve a definitive diagnosis. Material and methods. The results of the initial biochemical tests obtained in 35 children diagnosed of respiratory chain or pyruvate metabolism defects were reviewed. The efficiency of basal determinations (lactate, pyruvate, ketone bodies, amino and organic acids and carnitine), cerebrospinal fluid (CSF) analysis, and dynamic tests (exercise, glucose loading and glucose oxidation by lymphocytes) was discussed. Results. Plasma lactate and alanine, and CSF metabolites were the most informative measurements in basal status. Urine organic acids were very useful to confirm the initial suspicion. Glucose loading was the most informative and reliable challenge test for pediatric population, while exercise test was especially useful for older children with fatigability or peripheral nervous system involvement. Conclusions. Glucose oxidation by lymphocytes might be applied when the other dynamic tests can not be performed or are not informative.