Measurement of lactate in cerebrospinal fluid in investigation of inherited metabolic disease

Measurement of lactate concentrations in cerebrospinal fluid (CSF) has been suggested as part of the investigation of inborn errors of the electron transport chain, but little information exists regarding the reference range in children or the relationship between CSF and plasma concentrations. In 39 children without bacterial meningitis, diabetes, or recent seizures, we determined that the median (range) lactate concentrations in CSF and plasma collected concurrently were 1.4 (0.8-2.2) and 1.5 (0.6-2.3) mmol/L; the regression equation was CSF lactate = (0.38+/-0.06) plasma lactate + 0.83 (r2 = 0.14). In 8 of 11 (73%) children with electron transport chain defects, CSF lactate was > or =3.0 mmol/L; however, 2 of these 8 had a normal plasma lactate concentration. CSF lactate was also increased in 2 children with nonketotic hyperglycinemia. The finding that CSF lactate concentrations may be increased despite a normal plasma lactate value in children with electron transport chain defects is an important clue to the diagnosis of these disorders.