Relationship between lactate and thiamine-responsive disorders in hospitalised infants and children in Lao PDR: secondary analysis of a prospective cohort study.

Background: Lactate is a by-product of thiamine-deficient cellular metabolism, and hyperlactataemia can indicate severe illness. However, little is known about the clinical significance of hyperlactataemia in thiamine deficiency disorders.
Aim: To describe the relationship between whole-blood lactate level and thiamine-responsive disorders (TRDs) in children with signs/symptoms of thiamine deficiency in a high-risk region.
Methods: This is a secondary analysis of data from the Lao Thiamine study, a prospective cohort study which enrolled hospitalised infants and children (aged 21 days to <18 months) who had at least one sign or symptom suggestive of thiamine deficiency in Lao PDR. Therapeutic thiamine was administered, and clinical evaluations were completed at several time-points over the next 72 h. Three paediatricians reviewed individual case reports to evaluate clinical response to thiamine and assigned TRD status. Data from 402 children were analysed by logistic regression and predictive modelling to examine the relationship between hyperlactataemia and TRDs.
Results: Baseline hyperlactataemia (lactate >4.0 mmol/L) was associated with an increased odds of clinical improvement after thiamine administration [OR (95% CI) 2.32 (1.28-4.45), p  = 0.007]. Baseline hyperlactataemia was a significant predictor of thiamine deficiency (thiamine diphosphate <40 nmol/L) [area under the receiver operating curve (95% CI) 0.76 (0.67-0.84), p  < 0.001], and increased odds of mortality [OR (95% CI) 3.51 (1.38-8.94), p  = 0.009].
Conclusions: In children with signs/symptoms of thiamine deficiency, hyperlactataemia is associated with a favourable clinical response to thiamine, biochemical thiamine deficiency, and increased odds of mortality. Lactate may be useful in identifying children who might benefit from therapeutic thiamine.