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 (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 =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.