Abstract Although hereditary fructose intolerance (HFI) is an inborn error of fructose metabolism that classically presents at infancy, the diagnosis is often missed or delayed. In this study, we aimed to develop tools to facilitate the diagnosis of HFI. The intake of fructose‐containing food products, that is, fruit, fruit juice and sugar‐sweetened beverages, was assessed by a 3‐day food diary in adult HFI patients (n = 15) and age, sex, and BMI‐matched controls (n = 15). Furthermore, glycosylation of transferrin was examined using high‐resolution mass spectrometry and abnormally glycosylated transferrin was expressed as ratio of normal glycosylated transferrin. We found that the sensitivity and specificity of the 3‐day food diary for the intake of at least one fructose‐containing food product were both 100%. Both mono‐glyco:diglyco transferrin and a‐glyco+mono‐glyco:di‐glyco transferrin were greater in HFI patients and had a high‐discriminatory power (area under the receiver operating characteristic curve: 0.97 and 0.94, respectively). In this well‐characterized cohort of adult HFI patients, the 3‐day food questionnaire and the glycosylation pattern of transferrin are valuable tools to facilitate the recognition and diagnosis of HFI in adult patients.
