Supplementary Material for: Preterm Glycosuria – New Data from a Continuous Glucose Monitoring System

<b><i>Background:</i></b> Careful control of glucose homeostasis is essential for infants with very low birth weight (VLBW). In clinical practice, blood and urine glucose levels are monitored; however, their correlation has not been fully investigated in VLBW infants. <b><i>Objectives:</i></b> To evaluate the correlation between interstitial fluid glucose concentration (ISFG), glycosuria, and urine output among VLBW infants through continuous glucose monitoring (CGM). <b><i>Methods:</i></b> A prospective, single-center, open cohort study enrolled 74 VLBW infants with a mean birth weight of 1,066 g. CGM (Guardian Real-Time CGM®; Medtronic, Northridge, CA, USA) was used to measure glucose. The urine output was calculated using 4-hour intervals. Reagent strips were used for semiquantitative measurement of glycosuria. <b><i>Results:</i></b> The CGM delivered 102,334 glucose measurements. 2,684 urine samples were checked for glycosuria, of which 92.06% remained negative. Corresponding glycemia in samples without glycosuria remained normoglycemic (median 103 mg/dL; 10–90th percentile 80–144 mg/dL). The median glucose concentrations for samples in ascending glycosuria categories 1+, 2+, 3+, and 4+ were 152, 181, 214, and 222 mg/dL, respectively. A moderate correlation between ISFG and urine output was found for categories ≥1+ (<i>r</i><sub><i>s</i></sub> = 0.56; 95% confidence interval 0.42–0.68; <i>p</i> < 0.001). The urine output was significantly lower when glycosuria was absent (<i>p</i> < 0.05). Polyuria was observed only in glycosuria 4+ (median urine output 9.9; interquartile range 7.4–12.2 mL/kg/h). <b><i>Conclusions:</i></b> The renal glucose threshold in VLBW infants is between 150 and 180 mg/dL. A negative result for glycosuria is a reliable screening test to exclude hyperglycemia. Occurrence of glycosuria ≥1+ is an indication to test blood glucose.