The decision-making levels of urine tetrasaccharide for the diagnosis of Pompe disease in the Turkish population

Background: Recently, urinary excretion of the tetrasaccharide 6-alpha-D-glucopyranosyl-maltotriose (Glc4) has been proposed as a marker for the diagnosis and monitoring of Pompe disease (PD). We aimed to determine the reference intervals and reliable decision-making levels of urine tetrasaccharide concentrations for the diagnosis of infantileand late-onset Pompe patients in the Turkish population. Methods: In this study, nine patients with PD (five of them with late-onset PD [LOPD]) and 226 healthy individuals (aged 0-64 years) were included. Urine Glc4 concentrations were determined using the ultra-high-performance liquid chromatography (UHPLC) tandem mass spectrometry (MS/MS) method. Results: Our data showed that the urine tetrasaccharide levels decreased with age in healthy individuals (p < 0.001, r = -0.256). It was higher especially during the first year of life compared to that in the elder subjects. The tetrasaccharide level of Pompe patients was higher compared to that of healthy controls of the same age: 99 +/- 68 mmol/mol creatinine for infantile onset vs. 4.0 +/- 3.0 mmol/mol creatinine for healthy controls of the same age group and 12.1 +/- 17.4 mmol/mol creatinine for late onset vs. 1.7 +/- 1.2 mmol/mol creatinine for healthy controls of the same age group. Conclusions: The results of this study showed that the reference intervals of tetrasaccharide in urine changed over time; therefore, it is critically important to define agebased decision levels for the diagnosis of LOPD.