For symbols of metabolites if the differences were greater than .0003 proportional m/z units (m/z difference divided by m/z value) then the symbol was labeled "circa" after the atomic composition. 

For description of metabolites if the proportional difference of the m/z ratio between Evan's EPFL Polar metabolite assignments and RTI assignments was very low (<.0001 proportional m/z units) then the symbol and description was taken directly from Evan's metabolite file, but if differences were between 0.0001 and about .0003 proportional m/z units then the descriptions were labeled "Putative" . If the differences were greater than .0003 units, then the descriptions were labeled "Provisional". For example, "Provisional assignment. Vanilpyruvic acid is a catecholamine metabolite and precursor to vanilactic acid. Accumulation in urine is indicative of Aromatic L-aminoacid decarboxylase deficiency (PMID 16288991)." 

 by Rob Williams and Arthur Centeno, Aug 25, 2014