Assay of D-lactate in urine of infants and children with reference values taking into account data below detection limit

Accumulation of D-lactic acid produced by intestinal bacteria such as strep tococci and lactobacilli has been extensively studied in ruminants [1-4], I n humans an increased production of D-lactate by intestinal bacteria under pathological conditions such as the short bowel syndrome can cause metaboli c acidosis [5-8]. Since the lactate assays routinely used only measure L-la ctate we developed a sensitive method of D-lactate quantification and estab lished reference values in spot urines of infants and children (0 to 4 year s of age), The enzymatic method with fluorimetric quantification of NADH is linear up to 2 mmol/l. It has a detection limit of 3.4 mu mol/l. Among str ucturally related organic acids an interference was found only for L-lactat e and DL-2-hydroxybutyrate at concentrations which are way beyond their phy siological excretion. One hundred and sixty five spot urines of healthy Swi ss (S), Austrian (A), German (G) and Chilean (CHI) infants aged from 0 to 4 years were analyzed. The distribution of the data is close to a lognormal one. Values below the detection limit were simulated and age groups were fo rmed. In all populations D-lactate excretion was found highest during the f irst year of life; it declines with age during infancy and remains stable f rom 2.5 to 4 years of age, We show that D-lactate is excreted physiological ly by healthy infants and children below 4 years of age and present referen ce values for D-lactate excretion which show some differences between the p opulations tested. (C) 2000 Elsevier Science B.V. All rights reserved.