Response to “Methanol and ethylene glycol acute poisonings – predictors of mortality”

To the Editor:

I read with interest the study performed by Coulter et al.¹ recently published in Clinical Toxicology. Their aim was to evaluate the relationship between the three biomarkers (anion gap, osmolal gap, and pH) after methanol and ethylene glycol ingestion and clinical outcomes to determine which are prognostically useful. Therefore, they conducted a literature search in Medline and Embase and extracted the reports of poisoning with either methanol or ethylene glycol that had reported at least one of the three abovementioned biomarkers. They found a total number of 119 (21 dead) and 88 (19 dead) cases of methanol and ethylene glycol poisoning, respectively, from 14 articles. After statistical analysis of the data, they concluded that after methanol ingestion, a high osmolal gap and anion gap, and a low pH (< 7.22) were associated with a higher mortality rate with pH having the highest predictive value. It seems that they might have missed at least four articles on methanol toxicity – compatible with their inclusion criteria – in their literature search citing 285 patients, of whom 65 had died (Table 1).^2–5 In other words, they have evaluated a total of 119 cases while they have possibly missed 285. Their conclusions may, therefore, be questionable at least regarding methanol poisoning. Thanks for this interesting study.

Table 1 The published articles related to the prognostic factors of methanol poisoning that might have been missed by the authors.¹

Published article (year)	Authors	Number of the patients studied (dead)	Prognostic factors for lethality or permanent sequelae (based on Coulter, et al. inclusion criteria)
1979	Naraqi S, et al.	28 (4)	Prolonged acidosis (2)
2005	Hovda KE, et al.	51 (9)	Severe metabolic acidosis (pH < 6.9) (3)
2007	Paasma R, et al.	111 (25)	Degree of metabolic acidosis (4)
2011	Sanaei-Zadeh H, et al.	95 (27)	Median pH of 7.16 and 6.94 in survivors and non-survivors, respectively (5)