Letters to the editor

We were interested to read the article by Yang et al¹. which concluded that total antioxidant status (TAS) in the serum was not a significant influence on the clinical outcome of patients with paraquat poisoning. Although the authors evaluated an impressive number of patients (n = 296) retrospectively, we believe the methods used were not appropriate to determine whether serum TAS influenced outcome.

The authors do not state precisely what the commercial kit they used to quantify TAS actually measured. Moreover, the sample for TAS was stored for an undetermined period at −70°C but the authors do not provide information as to whether storage could have influenced their results. The authors took only one blood sample from each patient and that was at admission. As the mean time that had elapsed between ingestion and admission was 15.4 ± (SD) 25.3 h, there is a substantial difference between patients in regard to the time post-ingestion when the blood sample was drawn, which will have influenced the results. This aspect is not discussed by the authors. With normal kidney function, peak lung paraquat concentrations are reached within 5–7 h after ingestion (in renal failure peak lung concentrations are higher and are observed at a later time because paraquat renal excretion is reduced). Thus, the time elapsed between ingestion of paraquat and sampling for TAS is relevant. The authors state correctly that serum TAS concentrations are much lower than in lung tissue. Consequently, the authors' blood sampling strategy could have had a considerable impact on the ability to detect changes in serum TAS concentration.