Is the Measurement of Serum Formate Concentration Useful in the Diagnostics of Acute Methanol Poisoning? A Prospective Study of 38 Patients

Abstract

The aim of this article was to study the role of serum formate (S-formate) in diagnosing methanol poisoning. A prospective study was undertaken of 38 patients from the Czech methanol mass poisoning in 2012 -median age 51 [interquartile range (IQR) 37-62] years with confirmed methanol poisoning. S-formate was measured enzymatically. The receiver operating characteristics (ROC) curve was used to examine the predictive ability of S-formate. Asymptomatic patients had median S-formate of 1.9 (IQR 1.5-2.4) mmol/L. The median S-formate was 15.2 (IQR 13.9-17.6) mmol/L in symptomatic subjects with visual disturbances, 15.4 (12.1-18.0) mmol/L in subjects with dyspnoea and 15.7 (IQR 12.8-18.5) mmol/L in comatose patients. The differences in serum formate concentrations in symptomatic patients depending on clinical features were not significant (all p > 0.05). Patients with long-term visual sequelae of poisoning had median S-formate of 16.1 ) mmol/L; with central nervous system (CNS) sequelae, patients had 15.9 (IQR 14.2-19.5) mmol/L. In lethal cases, the median S-formate was 15.2 (IQR 13.8-15.9) mmol/L. The probability of a poor outcome (death or survival with sequelae) was higher than 90% in patients with S-formate ≥17.5 mmol/L, S-lactate ≥7.0 mmol/L and/or pH <6.87. The ROC analysis showed that the corresponding areas under the curve (AUC) were 0.64 (0.44-0.85 CI 95%) for S-formate, 0.75 (0.56-0.93 CI 95%) for 'S-formate+S-lactate' and only 0.54 (0.38-0.69 CI 95%) for serum methanol, which is lower than for S-formate (p < 0.05). The measurement of S-formate is an important tool in the laboratory diagnostics and clinical management of acute methanol poisoning. S-formate ≥3.7 mmol/L can lead to the first clinical signs of visual toxicity, indicating haemodialysis. S-formate ≥11-12 mmol/L is associated with visual/CNS sequelae and a lethal outcome.Acute methanol poisoning remains a challenge for healthcare providers throughout the world because of its high mortality rate and serious health sequelae [1][2][3]. This poisoning generally occurs either intentionally through abuse or attempted suicide or unintentionally through misuse or accident [4,5]. It is a medical emergency in which the rapid administration of antidotes preventing formic acid formation as a toxic metabolite of methanol by blocking alcohol dehydrogenase (ADH) and the enhanced elimination of formate and methanol are crucial for successful treatment [6][7][8].Nevertheless, in cases of poisoning with toxic spirits containing mixtures of methanol and ethanol in adulterated strong alcoholic beverages, timely diagnosis is difficult due to the long latency period and late presentation to hospitals. Therefore, the onset of treatment is often delayed [7,9]. Serum concentrations of methanol in late-presenting patients can be low and even under the level of detection due to its biotransformation. On the other hand, serum concentrations of formic acid rise high above the upper reference limit of 0.4 mmol/L [9].Formate is one of the normal intermediates in human...

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