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 (IQR 14.3-19.9) 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.