Risk assessment of methanol poisoning in outbreaks not applicable to isolated cases

To the Editor:

We read with great interest the recent study by Paasma et. al. in the November issue of Clinical Toxicology, regarding prognostic indicators in methanol poisoning.¹ This valuable multicenter retrospective study demonstrated the importance of pH and coma as risk factors for mortality and discussed the emerging significance of respiratory compensation of acidosis.

While we applaud the authors’ generation of a prognostic chart for their patient population (Paasma et al., Fig. 2), we are concerned that there are factors that make the chart non-generalizable. The study population consists largely of clusters of people poisoned during methanol outbreaks in various countries and times. We worry that people involved in methanol outbreaks are fundamentally different from those who ingest methanol in other settings – either knowingly as a means of suicide or as an ethanol substitute, or unintentionally. For example, previous publications on the Norwegian 2002–2004 cluster from this study found that these subjects tended to be older (median age 53), with a high prevalence of alcoholism,^2,3 possibly influencing their outcomes. It is also conceivable that since victims of a methanol outbreak are unaware of the methanol ingestion, they may not provide historical clues on initial presentation, increasing the possibility of delays to diagnosis and treatment. Alternatively, people involved in a methanol outbreak from tainted “alcohol” may have improved prognosis because of the presence of antidotal ethanol in the liquor. With the multiple possible confounding factors related to outbreaks, we are apprehensive about applying their results to non-outbreak methanol-poisoned patients.

We would specifically like to caution against the use of Fig. 2 in making treatment decisions, particularly, as the authors note, “when triaging patients.” It is widely held that there is a role for hemodialysis in severe methanol poisonings, but its use has been conspicuously omitted from this study and the development of the risk-assessment chart. Interestingly, in a paper on the cohort from the 2001 Estonia outbreak, Paasma et al. note that patients received shorter duration of hemodialysis due to limited resources in the face of the high number of patients involved in the outbreak.⁴ Given the widespread use of hemodialysis for severe methanol poisoning, as well as its potentially insufficient use in resource-limited settings, its absence from any paper on severe methanol poisoning prognosis is unfortunate.

Clearly the authors have demonstrated that low pH and coma are indicators of poor prognosis. Although the risk assessment chart presented by the authors makes logical sense, we believe caution should be used when using it to determine mortality risk and should not be used in making triage or treatment decisions, especially in non-outbreak poisonings.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.