An enzymatic assay with formate oxidase for point-of-care diagnosis of methanol poisoning.

Gas chromatographic analysis for quantification of plasma methanol requires laboratory equipment and personnel, and it is typically unavailable in short time notice, especially in low- and middle-income countries. Detection of formate with the enzyme formate oxidase (FOX) is a promising method that can make the diagnosis of methanol poisoning simple and fast. The aims of this study were to test the sensitivity and specificity of a modified FOX-enzyme and to test the specificity of a point-of-care (POC)-model containing FOX-enzyme with samples from patients with metabolic acidosis. The sensitivity and specificity of FOX-enzyme in aqueous solution were evaluated with a spectrometer and by visual detection for colour change. Formate concentrations between 1 and 20 mmol/L were used to test sensitivity, and 18 potentially interfering substances were tested for specificity. The sensitivity of the FOX-enzyme was 100% and the specificity 97%. When specificity of the POC-model was tested, no false positives were detected. As such, the sensitivity and specificity of this modified FOX-enzyme for detection of formate were high. The results with this enzyme confirm the potential for its use in formate analysis as a fast diagnosis of methanol poisoning.