Fully automatic d-lactate assay using a modified commercially available method

Intestinal infarction is the fast-evolving endpoint of impaired blood perfusion to an intestinal segment which may have fatal outcome. Early diagnosis and treatment within 6 h reduce mortality. Currently, d-lactate is a promising biomarker, however, not available in the acute clinical setting. The aim of this study is implementation of d-lactate analysis in a routine clinical setting. We used a spectrophotometric method, based on enzymatic oxidation of d-lactate by d-lactate dehydrogenase (D-LDH) coupled to the reduction of nicotinamide-adenine dinucleotide (NAD⁺). The amount of NADH formed in this reaction is equivalent to d-lactate. The primary concern in this method is interfering NADH formed by oxidation of l-lactate by l-lactate dehydrogenase (L-LDH). A commercially available kit for d-lactate measurement was implemented on our existing automated routine laboratory equipment including pH-inactivation of L-LDH. Our setup fulfilled clinical quality goals. We were able to measure d-lactate with an acceptable performance of the analysis and a short turn-around time. The method can be used to distinguish between the expected cut-off for intestinal ischemia around 0.3 mM and the upper reference limit of 0.05 mM. With a turnaround time of just 9 min, the analysis has potential as a readily available detection of circulating d-lactate for early diagnosis of intestinal ischemia.