Test Details: This test is useful for investigating possible disorders of mitochondrial metabolism when used in conjunction with blood lactate collected at the same time to determine the lactate-to-pyruvate ratio. An elevated lactate-to-pyruvate (L:P) ratio may indicate inherited disorders of the respiratory chain complex, tricarboxylic acid cycle disorders and pyruvate carboxylase deficiency. Respiratory chain defects usually result in L: P ratios >20. A low L:P ratio (disproportionately elevated pyruvic acid) may indicate an inherited disorder of pyruvate metabolism. Defects of the pyruvate dehydrogenase complex result in L: P ratios <10.